WBEZ | traffic http://www.wbez.org/tags/traffic Latest from WBEZ Chicago Public Radio en When is Chicago-area traffic the worst? http://www.wbez.org/series/curious-city/when-chicago-area-traffic-worst-111374 <p><p>Traffic. It&rsquo;s something utterly mundane and expected, but when you&rsquo;re inching through a major city on a car or bus, road congestion can be a kind of personal hell.</p><p>&ldquo;I feel like a terrible commute is only terrible to the person who&rsquo;s living it,&rdquo; observes our question-asker, Esther Bowen. She&rsquo;s a resident of Chicago&rsquo;s Bucktown neighborhood who commutes about 45 minutes each way to her job in suburban Lemont. That&rsquo;s provided plenty of time for her to formulate this question for Curious City:</p><p dir="ltr" style="text-align: center;"><em>What factors influence daily, weekly, and seasonal traffic patterns in the Chicagoland region?</em></p><p>If you can&rsquo;t sympathize with Esther, you should know that traffic affects you, even if you don&rsquo;t drive or ride the bus. All the congestion on Chicago-area roads sucked up more than $6 billion in wasted time and fuel in 2011, according to the Texas A&amp;M Transportation Institute. That&rsquo;s third among the 101 metro areas they assessed.</p><p>Of course, a lot of that wasted time is in what commuters like Esther might consider &ldquo;typical&rdquo; traffic jams. And that&rsquo;s how we&rsquo;re going to help her: by laying out what the &ldquo;expected&rdquo; traffic patterns actually are. We&rsquo;ll then have officials and researchers account for these variations, as well as what contributes to road congestion in the first place.</p><p>We can&rsquo;t guarantee that this information will necessarily make Esther or any other commuter happy to be on the road, but maybe it can steer folks clear of any traffic-induced personal hell.</p><p><span style="font-size:24px;">Traffic pattern: A typical day, measured hour by hour </span></p><div class="image-insert-image ">It&rsquo;s no secret that the length of your commute can depend on what time you start it. Citing <a href="http://ops.fhwa.dot.gov/congsymp/sld004.htm" target="_blank">data from the Federal Highway Administration and elsewhere</a>, the Texas Transportation Institute&rsquo;s Bill Eisele says bottlenecks &mdash; simply more drivers on the roads than the roads can accommodate &mdash; are responsible for about 40 percent of all traffic congestion nationwide.</div><p>But when it comes to a typical day in the Chicago area, when do drivers hit the heaviest traffic?</p><div class="image-insert-image "><a href="http://www.dot.state.il.us/transportation-system/Network-Overview/highway-system/illinois-travel-statistics" target="_blank">Figures from the Illinois Department of Transportation</a> show that on average, the hours ending at 4 p.m. and 5 p.m have the highest share of the day&rsquo;s traffic on Northeastern Illinois&rsquo; interstate highways. The worst morning hour, which is not as heavy as the afternoon peak, is from 7 to 8 a.m.</div><div class="image-insert-image ">&nbsp;</div><div class="image-insert-image "><div class="image-insert-image "><div class="image-insert-image "><img alt="" class="image-original_image" src="http://llnw.wbez.org/styles/original_image/llo/insert-images/traffic by hour2.png" title="This chart depicts the most congested travel times in Northeastern Illinois. Peak hours are between 6 a.m. and 8 a.m., and between 4 p.m. and 6 p.m., with afternoon rush hour being generally more congested than morning rush hour. AADT means annual average daily traffic, collected from 18 sites throughout the region between 2010 and 2013 by the Illinois Department of Transportation. Click to learn more about the data." /></div></div></div><p>Why is the morning rush hour generally lighter than the afternoon-evening rush hours? <a href="http://nhts.ornl.gov/2009/pub/stt.pdf" target="_blank">Citing data from the Federal Highway Administration</a>, Nebiyou Tilahun, an assistant professor of urban planning at the University of Illinois Chicago, says it&rsquo;s because people are doing more than just commuting in the afternoon.</p><p>&ldquo;In percentage terms, commuting dominates over other types of trips in the morning. In the afternoon, it is one of several trip types that congest the roadway. Family and personal trips as well as social/recreation trips are made with more or almost equal frequency,&rdquo; he says.</p><p><span style="font-size:24px;">Traffic pattern: A typical week, measured day by day</span></p><div class="image-insert-image "><div class="image-insert-image "><img alt="" class="image-original_image" src="http://llnw.wbez.org/styles/original_image/llo/insert-images/traffic by day3.png" title="This chart depicts traffic trends by day in Northeastern Illinois. The red line indicates the annual average daily traffic, so any value higher than the bar represents higher than average travel times and vice versa. Click to learn more about the data." /></div></div><div class="image-insert-image "><p>The discrepancy between morning and evening rush hours is even most pronounced on Friday, which IDOT says is generally the heaviest traffic day of the week in the Chicago area.</p><p>&ldquo;Thursday and Friday tend to be our worst p.m. rush hours,&rdquo; says IDOT&rsquo;s Matt Daeda. &ldquo;Oddly enough, we&rsquo;ve noticed in the past few years during the summer months our a.m. [Friday] rush hour tends to be a lot lighter than the other days of the week.&rdquo;</p><p>They think that&rsquo;s due to people taking long weekends, working from home, or otherwise shifting toward a four-day work week in the summer months. IDOT Spokeswoman Carson Quinn says they&rsquo;re seeing this pattern start to emerge on summer Thursdays, too.</p><p>Seattle-based traffic data firm INRIX agrees that Friday evening&rsquo;s commute is the single worst of Chicago&rsquo;s week. But the Chicago area&rsquo;s worst commute day overall &ldquo;is a toss-up between Wednesday and Thursday,&rdquo; according to spokesman Jim Bak.</p><p><span style="font-size:24px;">Traffic pattern: A typical year, measured month by month</span></p><div class="image-insert-image "><img alt="" class="image-original_image" src="http://llnw.wbez.org/styles/original_image/llo/insert-images/traffic by month3.png" title="This chart depicts traffic trends by day in Northeastern Illinois based on data collected between 2010 and 2013 by the Illinois Department of Transportation. Click to learn more about the data. " /></div><p>Summer is the worst season for Chicago-area traffic, in part because of the increase in construction work. According to Bill Eisele of the Texas Transportation Institute, construction is the fourth-leading cause of road congestion and is responsible for 10 percent of traffic jams nationwide.</p><p>IDOT says average weekday traffic increases on all of the Chicago area&rsquo;s major highways during the summer, but by different amounts. The Stevenson (I-55) sees the biggest jump, with as much as 12 percent more traffic, while traffic on the Eisenhower (I-290) only increases by 3 percent. The Kennedy and Edens (I-90 and I-94) get 8 and 11 percent more clogged, respectively.</p><p>But fall also sees a significant uptick in travel times. Jim Bak, a spokesman for INRIX, relays this office adage about seasonal traffic patterns: &ldquo;Back to school, back to work, back to traffic.&rdquo;</p><p>&ldquo;On a seasonal basis, the biggest impact is school schedules,&rdquo; says Bak. &ldquo;Nationally, it can increase traffic congestion levels by up to 15 percent. In Chicago we see an annual lift of up to 10 percent.&rdquo;</p><p><span style="font-size:24px;">What about reverse commutes?</span></p><p>As a city dweller who treks out to the suburbs during business hours, our question-asker, Esther, is a so-called reverse commuter. Suburban development and job growth has taken off in recent decades. <a href="http://www.npr.org/2013/10/29/241350699/reverse-commutes-now-often-a-daily-slog-too" target="_blank">That has created a surge in urbanites with suburban occupations</a>, like Esther. So, naturally, she wants to know if her increasingly common arrangement results in less traffic compared to the traditional commute from the suburbs to the city.</p><p>&ldquo;In general the traditional commute still is heaviest, more often than not,&rdquo; says IDOT&rsquo;s Carson Quinn. But that&rsquo;s not the case for all local expressways. On the Edens Expressway (I-94), for example, northbound traffic is heaviest in the morning while southbound is worst in the evening, suggesting a flow of traffic away from downtown for the workday. The Kennedy (I-90) is the same.</p><p><span style="font-size:24px;">What contributes to traffic?</span></p><p>So that&rsquo;s the basic answer to Esther Bowen&rsquo;s questions about Chicago&rsquo;s worst hours, days and seasons for traffic. But what are the general factors that influence traffic patterns?</p><p>According to the Federal Highway Administration, the major contributors are what you might expect: Bottlenecks, or just the sheer number of cars on the road, make up 40 percent of congestion nationwide. Traffic accidents and related slow-downs cause about 25 percent, while bad weather is responsible for 15 percent of lurching road travel. Construction is the last major cause, at 10 percent. The remaining 10 percent is due to things like poor signal timing, special events (like sports games and festivals) and other lesser factors.</p><p>Chicago doesn&rsquo;t deviate much from that national average, according to Steve Travia &mdash; he&rsquo;s IDOT&rsquo;s <a href="http://www.dot.state.il.us/about-idot/idot-regions/idot-region-1/index" target="_blank">District 1</a> bureau chief for traffic, responsible for overseeing traffic management and reporting in the six-county greater Chicago area. Traffic engineers at IDOT&rsquo;s District 1 headquarters monitor regional traffic on a bevy of video and computer monitors, <a href="http://www.wbez.org/series/curious-city/how-do-reversible-lanes-kennedy-expressway-work-101384" target="_blank">switching the direction of express lanes</a> and dispatching crews to clear accidents.</p><p>Bottlenecks and the like are perennial leaders in causing congestion, a fact he says is due to some basic physics.</p><p>&ldquo;There&rsquo;s a break point. There&rsquo;s a capacity limit of how many cars will truly fit on a lane of pavement,&rdquo; says Travia. Depending on the types of vehicles, traffic signals, topography and other factors (beyond just the size of the road), that capacity can vary. But as you approach what IDOT calls &ldquo;saturation,&rdquo; traffic will begin to slow down. People can change their driving habits to a certain point but, Travia says, &ldquo;then you hit that magic number. ... And that&rsquo;s when it breaks down. That&rsquo;s when you start to get that accordion effect.&rdquo;</p><p>Traffic engineers call that &ldquo;disrupted flow&rdquo;, and it ripples out quickly. In fact, Travia says, every minute an accident blocks a lane of traffic adds roughly three minutes of congestion on that highway.</p><p style="text-align: center;"><a href="http://www.wbez.org/series/curious-city/when-chicago-area-traffic-worst-111374#jindra"><strong>Related: Guide to decoding traffic reports</strong></a></p><p>What about weather? It seems, given our polar vortices and generally volatile weather, Chicagoans would see weather higher up in the relative breakdown of Chicago&rsquo;s traffic factors. But Kermit Wies, deputy executive director for research and analysis at the Chicago Metropolitan Agency for Planning, says it appears only about 13 percent of Chicago&rsquo;s traffic congestion occurs when the weather is wet, snowy or icy. So while <a href="http://www.wbez.org/series/curious-city/just-how-bad-chicago-winter-109637">those long winters can be brutal</a>, and they do help to clog the roadways, they&rsquo;re not game-changers when it comes to the broadest traffic patterns.</p><p>There are also surprising forces behind traffic patterns.</p><p>&ldquo;If people have jobs, they have money to spend, resulting in not only more commuter traffic but also more traffic in general as people go out to have dinner, to shop, go to a movie or cultural event, etc.,&rdquo; says INRIX&rsquo;s Jim Bak. &ldquo;Even now when more people tend to shop online, the product eventually has to get to your house from a distribution center &mdash; that happens on a truck.&rdquo; &nbsp;That means more raw materials are being delivered to manufacturing plants, and more freight to stores as they replenish inventory to keep up with increased consumer demand.</p><p>Freight traffic also impacts Chicago&rsquo;s commuters directly. The Texas Transportation Institute&rsquo;s Bill Eisele put it optimistically: &ldquo;Chicago is an exciting, dynamic, multi-modal town.&rdquo; But that also means motorists in the Chicago area, which sees up to a quarter of the entire nation&rsquo;s freight traffic, have to deal with the added congestion of trucks and train crossings. TTI&rsquo;s Urban Mobility Report estimates truck congestion alone cost Chicago more than $1.7 billion in lost time and fuel in 2011, the most recent year for which they&rsquo;ve crunched the numbers.</p><p>Infrastructure improvements could help ease that pain, Eisele says, as could an increase in public transit ridership.</p><p>&ldquo;For critical high-volume routes (like expressways),&rdquo; says Kermit Wies, of the Chicago Metropolitan Agency for Planning, &ldquo;traffic managers will use <a href="http://www.travelmidwest.com/lmiga/home.jsp" target="_blank">Intelligent Transportation Systems</a> (ITS) such as in-road sensors and cameras to make real-time decisions to close ramps and upstream lanes, issue signboard messages or media blasts in an effort to keep delays to a minimum.&rdquo;</p><p>That response is improving constantly, building on a general slump in miles driven per capita.</p><p>In Cook County,<a href="http://www.dot.state.il.us/Assets/uploads/files/Transportation-System/Reports/OP&amp;P/Travel-Stats/Illinois%20Travel%20Statistics%202013.pdf#page=7" target="_blank"> annual vehicle miles traveled have declined</a> since 2009 (across the state, that figure peaked in 2004 at 108,910,000,000 miles.)</p><p>Probably better to focus on that than the time and money you&rsquo;re wasting the next time you&rsquo;re caught in a bad bout of congestion on Chicago-area highways.</p><p><img alt="" class="image-original_image" src="http://www.wbez.org/system/files/styles/original_image/llo/insert-images/esther%20bowen.jpg" style="float: left; height: 300px; width: 300px;" title="Photo courtesy Esther Bowen" /><span style="font-size:24px;">Who asked our question?</span></p><p>Esther Bowen&rsquo;s curiosity is both personal and occupational. She commutes from Chicago&rsquo;s Bucktown neighborhood to Argonne National Laboratory, where she has worked as a scientist in the soil and groundwater sampling division for nearly three years. The trip usually takes about 45 minutes in the morning and an hour on the way back after work. That&rsquo;s plenty of time for her scientific mind to wade through the reasons that I-55 might flow freely one day and clog up the next.</p><p><a name="data"></a>&ldquo;I do kind of hate that I waste that much time in traffic,&rdquo; she says. &ldquo;I feel like &mdash; psychologically &mdash; if I can understand why it is, it would help to deal with it.&rdquo;</p><p>Esther and her husband, Aaron, moved to Bucktown from Chicago&rsquo;s Lakeview neighborhood in part to shave time off her commute. She remembers one trip back from work when they lived in Lakeview took two hours, thanks to rain showers and a Cubs game.</p><p>Esther&rsquo;s parents still live in her hometown of Crystal Lake, Illinois &mdash; about 45 miles northwest of downtown Chicago &mdash; so substantial commutes factor into her personal life as well as her career.</p><p>Most of her friends live and work in the city, and she&rsquo;s not expecting sympathy from them. Instead, she says she just hopes to satisfy a personal curiosity.</p><p>&ldquo;I feel like a terrible commute is only terrible to the person who&rsquo;s living it,&rdquo; she says.</p><p><span style="font-size:24px;">The data driving our presentation</span></p><p>Charts in our presentation use the term Annual Average Daily Traffic, or AADT, which means traffic engineers measured the total number of cars in a year on a given road and divided by 365 days. We followed the Illinois Department of Transportation&rsquo;s format, so when AADT is above 100 percent, it means that time period experiences greater than average traffic.</p><p>Now, a few words on how traffic is measured, generally speaking. Even if you&rsquo;ve never nerded out over traffic engineering, this will be relevant if you&rsquo;ve ever used your phone to navigate on the road.</p><p>A lot of the information gathered by the federal and local transportation agencies comes from inductive-loop traffic detectors &mdash; magnetic loops embedded in the pavement of highways and some smaller streets. The devices measure the number and size of vehicles passing over them. From this information, traffic engineers glean travel times using mathematical formulas.</p><p><a name="jindra"></a>Luckily for traffic geeks, there is a lot more data out there these days. Many of us travel with mobile devices and, while we do, Wi-Fi, Bluetooth and GPS components log data about our location at any given time. Google and other companies use that information to estimate the flow of traffic, and then deliver that data back through map programs and services.</p><p><em>Chris Bentley is a freelance writer and reporter for WBEZ&rsquo;s Curious City. Follow him at<a href="http://twitter.com/cementley" target="_blank"> @cementley</a> and at <a href="http://cabentley.com" target="_blank">cabentley.com</a>.</em></p></div><p>&nbsp;</p><p><iframe class="scribd_iframe_embed" data-aspect-ratio="undefined" data-auto-height="false" frameborder="0" height="600" id="doc_75518" scrolling="no" src="https://www.scribd.com/embeds/181823840/content?start_page=1&amp;view_mode=scroll&amp;show_recommendations=true" width="100%"></iframe></p><p><em style="font-size: 10px;">The above guide was compiled by previous WBEZ traffic reporter Sarah Jindra. It details major highway routes around the city and could also help make sense of the traffic reports you hear on the radio.&nbsp;</em></p></p> Fri, 09 Jan 2015 11:40:00 -0600 http://www.wbez.org/series/curious-city/when-chicago-area-traffic-worst-111374 Are Chicago's shorter yellow lights unsafe, or just unfair? http://www.wbez.org/news/are-chicagos-shorter-yellow-lights-unsafe-or-just-unfair-110955 <p><p>Chicago&rsquo;s red light cameras are under increased scrutiny, after a <a href="http://www.chicagotribune.com/news/watchdog/redlight/"><em>Chicago Tribune</em> investigation</a> found glitchy cameras may have issued thousands of tickets in error. The report also found many yellow lights are slightly short of the city standard of three seconds.</p><p>WBEZ has been looking into yellow lights too &mdash; and we&rsquo;ve found something else. Many traffic experts say Chicago flouts industry best practices with how it programs its traffic control devices &mdash; and one engineer says it may be &ldquo;entrapping&rdquo; drivers into running red lights.</p><p><span style="font-size:22px;">Should I run? Should I stop?</span></p><p>Our inquiry started with Pavel Gigov, a North Side resident who, incidentally, is not a transportation engineer. Gigov drives a car, and like many of us, he&rsquo;s gotten a red light camera ticket or two. He got one in April at an intersection he normally drove through on his way home from work, and thought something was strange.</p><p>&ldquo;The light turned yellow and my immediate reaction was, OK, let me figure out what to do,&rdquo; Gigov recounted. &ldquo;And before I could actually even put my mind around what the decent thing to do is &mdash; should I run? should I stop? &mdash; it was already red and I was in the middle of the intersection.&rdquo;</p><p>The intersection was at W Peterson Ave. and N California Ave., in Chicago&rsquo;s West Ridge neighborhood. The streets are pretty wide: each has six or seven lanes across, and like many Chicago roads, the speed limit is 30 miles an hour.</p><p><iframe frameborder="0" height="450" src="https://www.google.com/maps/embed?pb=!1m16!1m12!1m3!1d209.6174687124326!2d-87.69939310755217!3d41.99043739075356!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!2m1!1scalifornia+ave+peterson+ave!5e1!3m2!1sen!2sus!4v1409930061367" style="border:0" width="600"></iframe></p><p><em>Gigov received his red light camera ticket at the intersection of W Peterson Ave. and N California Ave. Like many Chicago intersections, the streets have a speed limit of 30mph.</em></p><p>Gigov said the moment he crossed into the intersection, he saw the flash of the red light camera going off.</p><p>&ldquo;And I knew that there was something that was going to be in the mail pretty soon,&rdquo; he laughed.</p><p>Sure, enough, Gigov got a $100 ticket in the mail. He paid it, but still, he wondered: wasn&rsquo;t that yellow light kind of short?</p><p><span style="font-size:22px;">Is it safe? Is it fair?</span></p><p><a href="http://www.cityofchicago.org/city/en/depts/cdot/supp_info/red-light_cameraenforcement.html">Chicago&rsquo;s Department of Transportation says</a> the city&rsquo;s yellow light intervals &ldquo;fall within the guidelines of the Federal Highway Administration&rsquo;s Manual on Uniform Traffic Control Devices, and adheres to recommendations by the Institute of Transportation Engineers.&rdquo; That&rsquo;s half-true.</p><p>First, the true part: <a href="http://mutcd.fhwa.dot.gov/htm/2009r1r2/html_index.htm">the MUTCD does, indeed, recommend</a> that yellow lights fall between 3 and 6 seconds. At the intersection where Gigov got his ticket, a frame-by-frame video analysis of the traffic signal showed that the yellow light lasts exactly three seconds &mdash; the minimum recommended under the MUTCD guidelines.</p><p>But three seconds falls short of what the yellow light interval should be, if the city were to follow ITE recommendations as it claims. Gigov said he worries that in flouting best engineering practices, Chicago may put drivers at risk. Particularly at red light camera intersections, where each traffic violation could bring dollars into the city&rsquo;s coffers.</p><p>&ldquo;Are we trading in accidents for revenue?&rdquo; he said. &ldquo;Unfortunately in the City of Chicago, that&rsquo;s a legitimate question.&rdquo;</p><p>The city claims it implements a blanket policy on yellow light intervals, regardless of whether there&rsquo;s a red light camera: three seconds when the speed limit is 30mph or lower, and four seconds when it&rsquo;s 35mph or higher. &ldquo;Chicago&rsquo;s yellow times are more than adequate for a driver traveling the speed limit to react and stop safely,&rdquo; it states on the <a href="http://www.cityofchicago.org/city/en/depts/cdot/supp_info/red-light_cameraenforcement.html">CDOT website</a>. The policy bucks a growing trend among transportation agencies nationwide.</p><p>&ldquo;The idea of a constant time is not typical,&rdquo; said James Taylor, a retired traffic engineer in Indiana.</p><p>While there&rsquo;s no federal mandate that requires transportation agencies to follow a method in determining yellow light intervals, Taylor said more places are adopting a <a href="http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_731.pdf">mathematical equation</a> that has been developed by the Institute of Transportation Engineers.</p><p>&ldquo;It keeps getting more and more widely accepted,&rdquo; said Taylor, &ldquo;as opposed to the system you&rsquo;re talking about where we just say let&rsquo;s just make all of them three (seconds), or three-and-a-half, or something like that.&rdquo;</p><p>A 2012 <a href="http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_731.pdf">survey</a> of more than 200 transportation agencies in the U.S., Canada and Germany, found only 6 percent timed their yellow light intervals the way Chicago does. By contrast, the largest chunk &mdash; almost 40 percent &mdash; used the ITE equation.</p><p><span style="font-size:22px;">Using the ITE formula</span></p><p>The ITE formula for the length of yellow lights factors in the specific conditions of an individual intersection, such as speed limit and the grade of the road. It also uses numerical assumptions based on extensive field studies.</p><div class="image-insert-image "><img alt="Y=t+(1.47V/2a+64.4g)" class="image-original_image" src="http://www.wbez.org/system/files/styles/original_image/llo/insert-images/yellow-light-fomula-1.png" style="height: 64px; width: 200px;" title="" /></div><div class="image-insert-image ">Where:</div><div class="image-insert-image "><em>Y = total clearance period (in seconds)</em></div><div class="image-insert-image "><em>t = perception-reaction time (usually 1 second)</em></div><div class="image-insert-image "><em>V = 85th percentile approach speed (mph)</em></div><div class="image-insert-image "><em>a = deceleration rate (ft/sec&sup2;)</em></div><div class="image-insert-image "><em>g = percent of grade divided by 100</em></div><div class="image-insert-image ">&nbsp;</div><div class="image-insert-image ">The equation assumes a perception-reaction time, <em>t</em>, of one second for the average driver, based on field measurements. In other words, it takes about that long for a typical driver to see that the light has changed to yellow, and to decide what to do.</div><div class="image-insert-image ">&nbsp;</div><div class="image-insert-image ">The fraction shown in the equation calculates how long it should take to decelerate to a stop, based on a typical driver&rsquo;s approach speed (<em>V</em>), a comfortable deceleration rate (<em>a</em>), and the grade of the intersection. Traffic engineers recommend using the 85th percentile of approaching traffic to determine a typical approach speed. If that hasn&rsquo;t, or cannot, be measured, a commonly accepted approximation is to add 7mph to the speed limit. &nbsp;Field studies have also found that a comfortable deceleration rate, <em>a</em>, for drivers is 10 ft/sec&sup2;. In Chicago, the grade of the street, <em>g</em>, is negligible, so we assume it to be zero.</div><p>Plug the numbers in for the intersection where Gigov received his yellow ticket, and it yields a yellow light interval, <em>Y</em>, of 3.7 seconds &mdash; that is, 0.7 seconds longer than it actually lasts. Studies show that could significantly change outcomes at an intersection.</p><p>&ldquo;Increasing the yellow by one second would decrease violations by 50-60 percent, and reduce crashes by 35-40 percent,&rdquo; said Davey Warren, a transportation engineer who spent most of his career with the Federal Highway Administration.</p><p>That agency has been pushing transportation departments nationwide to adopt the kinematic equation. In fact, in 2012 it made a change to the MUTCD that would require agencies to switch to engineering practices to determine yellow light intervals by mid-June of 2017.</p><p>Many traffic engineers were surprised to hear that Chicago does not already use widely-accepted engineering practices to calculate its yellow light intervals.</p><p>&ldquo;There is a general rule with engineers, you should be following the best accepted practice unless they can document valid reasons for not doing so,&rdquo; said Warren.</p><p>WBEZ requested multiple times to interview someone at Chicago&rsquo;s Department of Transportation. The department didn&rsquo;t respond. The department also failed to respond to a request under the Freedom of Information Act for its programming instructions for traffic control devices.</p><p><span style="font-size:22px;">After the yellow, comes the all-red</span></p><p>But before you worry that the city&rsquo;s putting drivers at risk by skimping on yellow light times, there&rsquo;s a twist. In addition to recommending a mathematically-derived yellow light interval, transportation engineers also recommend something called an <em>all-red interval</em>. That&rsquo;s a brief moment after the yellow light, where the lights are red in <em>all directions</em>. It gives a chance for cars still caught in the intersection to finish crossing before the opposing traffic gets a green.</p><p>The ITE recommendation for the all-red interval has changed over time. However,a 2012 <a href="http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_731.pdf">study</a> by the National Cooperative Highway Research Board proposed the following guideline for the calculation:&nbsp;</p><div class="image-insert-image "><img alt="R=(W+L/1.47V)-1" class="image-original_image" src="http://www.wbez.org/system/files/styles/original_image/llo/insert-images/yellow-light-fomula-2.png" style="height: 59px; width: 200px;" title="" /></div><p>Where:</p><p><em>R = all-red clearance interval (seconds)</em><br /><em>W = intersection width (ft)</em><br /><em>L = length of vehicle (ft)</em><br /><em>V = 85th percentile approach speed (mph)</em></p><p>It&rsquo;s worth noting that there&rsquo;s some debate over subtracting the number 1 on the right side of this equation. The &nbsp;ITE contemplates both possibilities. The NCHRP study found in field studies that it typically takes one second for drivers to perceive and react to a change to green after the all-red interval. So in its conclusions, it recommends subtracting that reaction time, to keep traffic flow more efficient.</p><p>Across transportation engineering literature, the standard length of a vehicle, <em>L</em>, is 20 feet, and again, the approach speed is approximated by adding 7mph to the speed limit.</p><p>At Gigov&rsquo;s intersection, where the streets were approximately 60 feet wide, the formula above yields an all-red clearance interval of 0.47 seconds. That means a vehicle that was caught in the intersection when the light turned red, would still have about half-a-second to finish its transition before opposing traffic gets a green light.</p><p>It turns out, the actual all-red clearance interval at the intersection of W Peterson Ave and N California Ave alternates between one and two seconds. Both of these are much longer than the formula recommends.</p><div class="image-insert-image "><img alt="" class="image-original_image" src="http://www.wbez.org/system/files/styles/original_image/llo/insert-images/yellow-lights-2.png" title="" /></div><div class="image-insert-image "><em>At a typical intersection in Chicago, where speed limits are 30mph, the city sets yellow lights at three seconds, followed by an all-red clearance interval of at least one second. By comparison, best engineering practices recommends a yellow light of 3.7 seconds, followed by an all-red clearance interval of .47 seconds. Experts say that while the total clearance times are close (4 seconds and 4.17 seconds, respectively), the misallocation of time between the yellow and all-red intervals may entrap drivers into more violations.</em></div><div class="image-insert-image ">&nbsp;</div><div class="image-insert-image "><em>Data on actual yellow lights from CDOT&rsquo;s website and field measurements at intersection of W Peterson Ave. and N California Ave. Recommended calculations based on the<a href="http://www.ite.org/bookstore/IR-113.pdf"> kinematic equation</a> developed by the Institute of Transportation Engineers.</em></div><div class="image-insert-image ">&nbsp;</div><div class="image-insert-image "><span style="font-size: 22px;">&lsquo;Entrapping drivers into running red lights&rsquo;</span></div><div class="image-insert-image ">&nbsp;</div><div class="image-insert-image ">Together, the yellow light and the all-red interval add up to what&rsquo;s called a &ldquo;change period.&rdquo; That &ldquo;change period&rdquo; at the intersection where Gigov got his ticket equals the three-second yellow light, plus one or two seconds for the all-red interval -- a total of four or five seconds. Engineering practices would yield a nearly similar result: a 3.7 second yellow light, followed by 0.47 second all-red interval, totaling 4.17 seconds.</div><p>The difference is, Chicago shortens the yellow portion of the change interval, and lengthens the all-red portion.</p><p>&ldquo;So from a safety standpoint, it&rsquo;s probably OK, but the thing is they&rsquo;re misallocating the times,&rdquo; said Warren, &ldquo;and so they&rsquo;re basically entrapping drivers into running red lights.&rdquo;</p><p>In other words, Chicago&rsquo;s yellow light intervals may not be unsafe, but they may be unfair.</p><p>Gigov said if the city wants to win back public trust when it comes to its use of red light cameras, it should use to the most up-to-date engineering guidelines when it programs its traffic control devices.</p><p>&ldquo;You&rsquo;re the city of Chicago, and your fiduciary duty is to serve residents of the city, and not to increase the revenue in such a borderline shady way,&rdquo; said Gigov.</p><p>Last year, anger over red light camera tickets in Florida prompted a reexamination of yellow lights. It turned out, yellow lights in that state were also timed contrary to engineering formulas. So Florida&rsquo;s Department of Transportation mandated the lights be lengthened.</p><p>Gigov said he hopes Chicago will do the same.</p><p><em>Odette Yousef is WBEZ&rsquo;s North Side Bureau reporter. Follow her </em><a href="https://twitter.com/oyousef"><em>@oyousef</em></a><em> and </em><a href="https://twitter.com/WBEZoutloud"><em>@WBEZoutloud</em></a><em>.</em></p></p> Fri, 17 Oct 2014 08:11:00 -0500 http://www.wbez.org/news/are-chicagos-shorter-yellow-lights-unsafe-or-just-unfair-110955 Chicago: Weekend traffic closures September 20, 21 & 22 http://www.wbez.org/news/transportation/chicago-weekend-traffic-closures-september-20-21-22-108731 <img typeof="foaf:Image" src="http://llnw.wbez.org/main-images/road closed.jpg" alt="" /><p><p><strong>Filming a Paramount Pictures Movie aka Probably Transformers 4</strong><br />Saturday-Sunday<br />7am-Noon<br />2900 S. Damen Ave (Abandoned Silo Site) and Intermittent Traffic Pacing on SB/NB I-55 around Damen Ave.<br />Illinois State Police are going to control traffic on I-55 for large effects taking place on the silo site.<br />Helicopter will be in the area doing aerial photography.<br />Controlled explosions and visible fireballs will be taking place.</p><p><br /><strong>Red Bull Flugtag</strong><br />Saturday<br />Burnham Park - No street closures but expect traffic delays on South Lake Shore drive at 42nd st.</p><p><strong>Apple Fest - Family festival celebrating the beginning of fall - Lincoln Square</strong><br />Saturday<br />9am-5pm<br />Lincoln is closed between Leland and Lawrence</p><p><strong>Lakeview Taco Fest</strong><br />Saturday-Sunday<br />Southport is closed between Addison and Newport</p><p><strong>City Made Fest in Andersonville - First ever Local&rsquo;s only Festival</strong><br />Saturday - Sunday<br />Clark st between Argyle and Carmen</p><p><strong>Design Harvest - Celebration of design in West Town</strong><br />Saturday-Sunday<br />Grand Ave closed between Damen and Wood St<br />&nbsp;</p></p> Fri, 20 Sep 2013 09:39:00 -0500 http://www.wbez.org/news/transportation/chicago-weekend-traffic-closures-september-20-21-22-108731 Trouble with taxis http://www.wbez.org/series/curious-city/trouble-taxis-108523 <img typeof="foaf:Image" src="http://llnw.wbez.org/main-images/taxi thumbnail for timeline cms.jpg" alt="" /><p><p dir="ltr">Curious Citizen Dan Monaghan from Chicago&rsquo;s Wicker Park neighborhood says he can&rsquo;t recall ever seeing a taxicab pulled over. And, to him, that seemed kind of crazy, considering the number of &ldquo;close calls&rdquo; he says he&rsquo;s had with taxis as a bike commuter, driver and pedestrian.</p><p dir="ltr">&ldquo;It just seems lawless, like they can get away with anything,&rdquo; he says.</p><p dir="ltr">WBEZ&rsquo;s North Side bureau reporter Odette Yousef hopes data can tease out this claim, as well as answer Dan&rsquo;s core question. Odette&rsquo;s reported on <a href="http://www.wbez.org/cabbie%E2%80%99s-lawsuit-against-chicago-moves-forward-104355">issues some Chicago taxi drivers already have</a> with the city&rsquo;s regulations, as well as <a href="http://www.wbez.org/news/chicago-hunt-taxi-recruits-105421">cabbie recruitment</a>.</p><p><iframe frameborder="0" height="650" src="http://embed.verite.co/timeline/?source=0Am-AbC8HDbXMdG9NV0VtRURYRFpXS0dtOHZCdWRxa0E&amp;font=Bevan-PotanoSans&amp;maptype=toner&amp;lang=en&amp;height=650" width="100%"></iframe></p></p> Mon, 26 Aug 2013 12:40:00 -0500 http://www.wbez.org/series/curious-city/trouble-taxis-108523 Traffic congestion's carbon footprint http://www.wbez.org/blogs/chris-bentley/2013-02/traffic-congestions-carbon-footprint-105367 <p><p><a href="http://www.flickr.com/photos/carusophoto/4017256834/" target="_blank"><img alt="" class="image-original_image" src="http://www.wbez.org/system/files/styles/original_image/llo/insert-images/traffic-by-john-caruso-via-flickr.jpg" title="Traffic on I-94 from the Van Buren street bridge. (John Caruso via Flickr)" /></a></p><p>Traffic congestion produced 56 billion pounds of carbon dioxide (CO<sub>2</sub>) pollution in 2011 &mdash; roughly equivalent to the emissions from the electricity use of 3.8 million homes for one year &mdash; according to the Texas A&amp;M Transportation Institute&rsquo;s <a href="http://mobility.tamu.edu/ums/">Urban Mobility Report</a> released Tuesday.</p><p>While the report&rsquo;s main innovation was <a href="http://www.wbez.org/news/report-chicago-traffic-bad-leave-early-105360">a new metric that predicted the unpredictably of metro area traffic</a>, it also included for the first time an estimate of the additional CO<sub>2</sub> emissions attributed to traffic congestion. That does not include emissions from cars traveling when roadways are uncongested.</p><p>Transportation is responsible for roughly one third of U.S. carbon emissions, making it the second largest-emitting sector (behind electricity generation). Worldwide transportation represents <a href="http://www.sciencedaily.com/releases/2009/07/090727080836.htm">20 percent</a> of total energy consumption.</p><p><a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=2&amp;cad=rja&amp;ved=0CEAQFjAB&amp;url=http%3A%2F%2Fwww.uctc.net%2Faccess%2F35%2Faccess35_Traffic_Congestion_and_Grenhouse_Gases.shtml&amp;ei=pasRUbSzLO7xyAHCnIH4Cg&amp;usg=AFQjCNH6HMuR6qigf7k9-9XQbAVN5T1IIA&amp;sig2=FlwgZ9weMMItgkzxSXWgLQ&amp;bvm=bv.41934586,d.aWc">It is difficult to measure</a> congestion&rsquo;s contribution to national carbon emissions &mdash; estimates are sensitive to highly variable factors like driving behavior, vehicle and roadway types, and local traffic conditions &mdash;but the report&rsquo;s stab at quantifying the issue could help further visualize a largely ignored pollution problem.</p><p>Noted climate scientist <a href="http://www3.geosc.psu.edu/people/faculty/personalpages/ralley/">Richard Alley</a> has pointed out that if the roughly 1 pound of CO<sub>2</sub> per mile that cars emit were &ldquo;horse ploppies,&rdquo; instead of invisible gas, every road in the country would be underneath an inch of poop within one year.</p><p>&ldquo;Fuel wasted in congested traffic reached a total of 2.9 billion gallons &mdash; enough to fill the New Orleans Superdome four times,&rdquo; the report reads. That is the same as in 2010, but less than the 3.2 billion gallons wasted in 2005.</p><p>There are a few key ways to improve the fuel efficiency of cars. Scientists and engineers are working on lighter vehicles, more efficient engines, and engines that run on alternative fuels. But advocates of policy solutions say just changing driving patterns can also have a significant impact.</p><p>The Chicago Metropolitan Agency for Planning touts <a href="http://www.cmap.illinois.gov/congestion-pricing">congestion pricing</a> as one such intervention, citing <a href="http://www.cmap.illinois.gov/policy-updates/-/blogs/economic-impacts-of-express-toll-lanes-in-the-chicago-region">long-term economic impacts</a> to boot &mdash; CMAP&rsquo;s Jesse Elam <a href="http://www.wbez.org/programs/afternoon-shift/2013-02-05/afternoon-shift-road-rage-105356">talked about their plan on The Afternoon Shift</a>.</p><p>Research out of the <a href="http://www.uctc.net/papers/846.pdf">University of California at Riverside</a>, which has its fair share of traffic, found metering ramp entry, lowering average driving speeds to 55 mph and reducing traffic congestion through variable speed limits could each potentially lower CO<sub>2</sub> emissions 7 to 12 percent. The combined effects of one or more of these changes could be greater, their report said.</p><p>&ldquo;Including CO<sub>2</sub>&nbsp;emissions into the [Urban Mobility Report] provides another dimension to the urban congestion problem,&rdquo; said researcher and co-author David Schrank in <a href="http://mobility.tamu.edu/ums/media-information/press-release/">a press release</a>.&nbsp; &ldquo;It points to the importance of implementing transportation improvements to reduce congestion.&rdquo;&nbsp;</p><p>Researchers said they plan to include more metrics of air quality in future reports.</p></p> Wed, 06 Feb 2013 05:00:00 -0600 http://www.wbez.org/blogs/chris-bentley/2013-02/traffic-congestions-carbon-footprint-105367 Thanksgiving traffic deaths down from last year http://www.wbez.org/news/thanksgiving-traffic-deaths-down-last-year-104079 <img typeof="foaf:Image" src="http://llnw.wbez.org/main-images/traffic signs.jpg" alt="" /><p><p>The Illinois Department of Transportation (IDOT) announced traffic deaths over Thanksgiving weekend decreased 63 percent from last year.</p><p>Provisional data from IDOT&rsquo;s crash information unit reported three traffic deaths compared to eight deaths during the holiday in 2011.</p><p>Mike Claffey, a spokesman for IDOT, said even though traffic deaths are down there&rsquo;s still work to be done.</p><p>&ldquo;This weekend there was three too many crashes and the campaign is to drive the number to zero,&rdquo; Claffey said. &ldquo;We want to keep the pressure on anybody who thinks of driving under the influence and we want to keep reminding folks... buckle up.&rdquo;</p><p>To help cut down on the number of traffic deaths this holiday season, IDOT launched a partnership with law enforcement called the &quot;Drive to Survive&quot; campaign.</p><p>Police will be out in force, pulling drivers over who are not wearing seatbelts and cracking down on drunk driving through the end of the year.</p><p>Claffey said the department has boosted its effort to educate people about driving safety, including highway signs that tally the number of traffic deaths to date this year.</p></p> Wed, 28 Nov 2012 14:11:00 -0600 http://www.wbez.org/news/thanksgiving-traffic-deaths-down-last-year-104079 Top traffic bottleneck to get improvement study http://www.wbez.org/news/transportation/top-traffic-bottleneck-get-improvement-study-98501 <p><p>Illinois officials will begin engineering studies for reconstructing the "Circle Interchange," located west of Chicago's Loop.</p><p>The point at which the Kennedy, Dan Ryan and Eisenhower expressways and the Congress Parkway converge has been labeled the nation's top traffic bottleneck.</p><p>Gov. Pat Quinn said Monday the $40 million, two-year study will identify needed improvements, cost and construction schedule.</p><p>Quinn's Transportation Department wants suggestions from taxpayers in nearby neighborhoods and businesses, Chicago city officials, the Chicago Transit Authority and the University of Illinois at Chicago.</p><p>The interchange has not been improved in its 50-year history. It handles 300,000 vehicles daily -- 26,000 trucks -- which travel at below ideal speeds for more than 14 hours a day.</p><p>Preliminary analysis calls for additional lanes on key ramps.</p></p> Tue, 24 Apr 2012 09:58:00 -0500 http://www.wbez.org/news/transportation/top-traffic-bottleneck-get-improvement-study-98501 Speed cameras come to Chicago school zones, but do they work? http://www.wbez.org/episode-segments/2012-02-07/speed-cameras-come-chicago-school-zones-do-they-work-96163 <img typeof="foaf:Image" src="http://llnw.wbez.org/segment/photo/2012-February/2012-02-06/020712 Seg A1.jpg" alt="" /><p><p>Chicago lead foots beware: Yesterday, Illinois Governor Pat Quinn signed off on a plan that would allow the use of speed cameras in school zones and parks. Mayor Rahm Emmanuel says the move will protect children; critics argue the cameras are an excuse to bring in some much-needed revenue for the city.</p><p>WBEZ reporter Alex Keefe explained the details, and&nbsp;Kristen McQueary, who covers state politics for WBEZ and the Chicago News Cooperative, told <em>Eight Forty-Eight </em>what the plan says about Gov. Quinn's legislative style. Thomas Goetz, executive editor of <em>Wired </em>magazine, compares the Chicago plan to systems that use dynamic speed displays instead of cameras.</p></p> Tue, 07 Feb 2012 21:55:00 -0600 http://www.wbez.org/episode-segments/2012-02-07/speed-cameras-come-chicago-school-zones-do-they-work-96163 Naperville council votes to end red light cameras http://www.wbez.org/story/naperville-council-votes-end-red-light-cameras-93703 <img typeof="foaf:Image" src="http://llnw.wbez.org/archives/images/cityroom/cityroom_20100610_akeefe_1238416_Red _large.png" alt="" /><p><p>West suburban Naperville is ending it's red-light camera program. A split vote on Tuesday resulted in the council nixing the red light camera program. They cited statistics that show red light cameras have reduced collisions at some intersections.</p><p>But two of the city's three cameras must be removed during upcoming construction. Council members have debated whether it makes financial sense to keep the last camera.</p><p>Karen DeAngelis is the Director of Finance for the city of Naperville. She said the average net monthly revenue is $65,000 dollars from all three cameras. The average monthly maintenance is $29,000 dollars. DeAngelis said the remaining camera is at the least violated of all intersections, so it may not result in the city making money off of it.</p><p>Councilman Bob Fieseler said that's in part because motorists have become more cautious and there are now fewer violations.</p><p>"Let's take government out of the enforcement business until there's a problem," Fieseler said.</p><p>Fieseler said the question remains as to whether violations will creep back up without the cameras.</p><p>In January, Naperville will go back to catching motorists entirely the old fashioned way with police officers.</p><p>Stopping the camera program will pile an additional $200,000 dollars to the city's $1.9 million dollar shortfall in next year's budget.</p></p> Wed, 02 Nov 2011 19:27:00 -0500 http://www.wbez.org/story/naperville-council-votes-end-red-light-cameras-93703 Getouttamyway! (Thoughts on city traffic) http://www.wbez.org/story/2011-06-14/getouttamyway-thoughts-city-traffic-87827 <img typeof="foaf:Image" src="http://llnw.wbez.org/npr_story/photo/2011-June/2011-06-14/380379732_8d3a32beab.jpg" alt="" /><p><p>I've been to Rome, so I've seen the <a href="http://www.youtube.com/watch?v=pPpihEKJk5Y&feature=player_embedded" target="_blank">dark side</a>: a traffic intersection where everybody decides to get where they're going at the same time, so no one gets anywhere. Cairo might be even worse. This isn't a parking lot, <em>it's a street...<br /></em></p><p>City people are always pushing; if you think you won't get caught, you keep moving. The rules don't matter. The signs don't matter.</p><p>But the amazing thing is, in most towns, even though people are constantly pushing their luck, taking crazy chances in traffic, they don't die, they don't get hurt. They get where they're going. And that's a miracle.</p><p>Just take a look at this video, created by New York designer (and School of Visual Arts grad student) Ron Gabriel, who went to a Manhattan intersection, 28th Street and Park Avenue, and watched cars, trucks, bicyclists and pedestrians skirting inches from each other with matter-of-fact ease.</p><p>The near misses (or the exquisite ballet between people and machines) is both maddening and thrilling, especially when Gabriel adds spatial graphics, sound effects and the theme from TV's "Peter Gun" by Art of Noise. This video will make you hate bikers.</p><p></p><p>And so it has always been. Traffic scholar Tom Vanderbilt <a href="http://www.nytimes.com/2008/08/10/books/chapters/traffic-chap.html?pagewanted=3">wondered</a> how pedestrians, chariots and carts negotiated the very narrow streets of ancient Pompeii.</p><p><blockquote></p><p>The tourist wonders: Was it a one-way street? Did a lowly commoner have to reverse himself out of the way when a member of the imperial legions came trotting along in the other direction? If two chariots arrived at an intersection simultaneously, who went first?</p><p></blockquote></p><p>The answer, says traffic archaeologist <a href="http://www.pompeiana.org/Research/Streets_Research/Streets_Research.htm">Eric Poehler</a>, is Pompeians improvised. There weren't road signs. There were one-way streets. But, studying the "wear patterns at corners as well as the stepping stones set up for pedestrians," Poelher says people just learned to get out of each others way. Just like today.</p><p><hr /></p><p><em>The newest book that explores the history of traffic in old New York, London and ancient Rome comes from Tom Vanderbilt. It's called</em> "Traffic: Why We Drive the Way We Do (And What It Says About Us<em>)" from Knopf 2008. And probably the most dramatic (brand new) essay on at traffic safety comes from Casey Neistat, a New York City filmmaker who purposefully ran into Manhattan potholes, construction sites, moving vans, even a police car to protest a $50 ticket he got for riding outside the bicycle lane. His point: riding in bicycle lanes is dangerous for bicyclists, so unsafe that bicycle lanes aren't worth it. My point: Casey has to mightily (you won't believe what he does) exaggerate to make his case, which makes me wonder if he's got a case, but, if you don't mind the occasional swear word and someone doing stunts without a helmet, Casey's video, </em>"What Happens When You Ride in a Bike Lane<em>" is, in its inane way, delightful. </em> <div class="fullattribution">Copyright 2011 National Public Radio. </p> Tue, 14 Jun 2011 09:59:00 -0500 http://www.wbez.org/story/2011-06-14/getouttamyway-thoughts-city-traffic-87827