Chicago officials say they have decided to leave at least one parking lane on both possible routes of the city’s most ambitious bus project. The officials say they have also ruled out narrowing sidewalks along those routes.

The details emerged Tuesday night at the first of three public meetings the Chicago Transit Authority is holding this week to unveil design alternatives for “bus rapid transit” along 21 miles of both Ashland and Western avenues.

All designs the city says it’s considering for the corridor include around-the-clock dedicated lanes for the buses and pre-boarding fare collection. Those features would distinguish the project from an express line the city started building along the South Side’s Jeffery Boulevard in August. That service, called “The Jeffrey Jump,” is set to start early next month.

The Ashland and Western routes would also include traffic lights rigged to favor the buses and station enhancements such as bike racks and electronic bus-tracking signs.

But CTA and Chicago Department of Transportation officials say they have yet to decide on a range of features that would shave travel times for riders. Those include station platforms and buses equipped with extra-wide doors for quick boarding.

Other big questions concern whether to put the bus lanes down the middle of the avenues or along the sides, whether each side would have one non-bus travel lane or two, whether to keep parking on both sides, whether to reserve space for a landscaped median, and whether to limit left turns.

About three-dozen Chicago residents attended Tuesday’s session, held in a Humboldt Park church. The meeting included a brief slide show by Scott Kubly, a top CDOT official. “We’re looking at what happens if we remove a travel lane and we want to hear back from you all [about] how you perceive those impacts,” Kubly told them.

Fernando Benavides, a resident of the nearby Belmont Cragin neighborhood, said the plan to preserve at least one parking lane on each avenue was not enough. “Elimination of lanes for cars and parking, my God, that’s just going to create a lot of traffic,” he said.

Other residents voiced support for any steps to speed up transit service. New city estimates show the Ashland and Western buses averaging as fast as 16-18 miles per hour, almost rivaling CTA Red Line trains, which would average 21 miles per hour if slow zones were repaired. The BRT lines would run between Howard Street on the north and 95th Street on the south.

The other two meetings are set for Wednesday at Lindblom Math and Science Academy, 6130 S. Wolcott Ave., and Thursday at Lane Tech College Prep High School, 2501 W. Addison St. Both will take place at 5:30 p.m.

Officials say they will present final decisions on the design alternatives this winter. The city is studying the alternatives using a $1.6 million grant from the Federal Transit Administration, part of the U.S. Department of Transportation. Construction would depend on further federal funding.