photo by: Mike Yoder/Journal-World File Photo

Traffic moves along Iowa Street near 23rd Street in this file photo from 2008.

Upcoming changes to traffic signals along some of the city’s main corridors will aim to decrease the time motorists spend sitting behind red lights and improve traffic flow throughout the city.

Olsson, an engineering and design firm hired by the city, is making adjustments to the timing and function of traffic signals following an approximately yearlong study of traffic patterns. The changes will be made to 23rd Street/Clinton Parkway and Iowa Street and will be implemented over the next two weeks beginning on Tuesday.

Josh Carson, spokesperson for the city’s Municipal Services and Operations department, said in an email to the Journal-World that intersections are currently set up using a vehicle detection system and that the changes will allow motorists to travel to 23rd Street/Clinton Parkway and Iowa Street more efficiently and with more consistent travel times.

“Motorists should be able to travel through portions of the priority corridors without hitting multiple back-to-back yellow or red lights,” Carson said.

In May 2019, the Lawrence City Commission approved $250,000 in funding for the citywide traffic signal coordination and timing study to improve the flow of traffic throughout the city. At that time, city staff noted that the time it takes to drive across the city and the frequent stops required have been cited as a source of frustration by many residents in citizen surveys, letters to the editor and correspondence with city officials. The highest priority streets for improved traffic flow were Sixth Street, 23rd Street/Clinton Parkway and Iowa Street, according to a memo to the commission. The changes to Sixth Street were already implemented earlier this year.

As part of the study, Olsson analyzed the city’s stoplight timing schedule, updated clearance times for each signal type for motorists and pedestrians, and developed coordinated signal timings for peak traffic periods throughout the day, according to a city news release. The new signal coordination is anticipated to reduce overall vehicle stops, vehicle delay, and as a result improve vehicle emissions for the city.

Carson said that to prioritize traffic flow on major arterial streets, drivers may notice a small increase in wait time when crossing or turning onto them from collector streets with signals. He said the increase will be most noticeable during the morning and afternoon rush hours, which have a longer cycle time. In addition, the city has changed the standard for pedestrian crossing from 4 feet per second to 3.5 feet per second, giving pedestrians more time to cross intersections. Carson said that change could add an additional two or three seconds for crossing small collector streets and eight to 10 seconds for larger arterial streets with multiple turn lanes at the intersection.

“This should improve safety and pedestrians are likely to feel less rushed when crossing those wider arterial (streets),” Carson said.

Changes to timings on Sixth Street were implemented in May, according to the release. Timing changes on Iowa Street are tentatively scheduled to begin on Tuesday and be completed on Wednesday. Changes on 23rd Street/Clinton Parkway are scheduled to begin on Wednesday and be completed on Thursday. Fine-tuning to both corridors will begin Thursday and will continue through next week.

As a result of the study, the city will also be discontinuing use of the current overnight signal function for many stoplights, which all currently flash yellow or red in the late night and early morning hours. The flash function will be replaced with the normal signals, but with different timings that rely on vehicle and pedestrian detection devices to activate the signal.

A report on the work of Olsson and the city to improve the stoplight timings will be provided to the City Commission this winter. The report will summarize the changes and their effect on travel time in the city. Those results will help guide the ongoing process of equipment upgrades and the improvement of stoplight timings and coordination throughout the city, according to the release.