Getting Around: As Kennedy traffic swells, reversible lanes lose their magic

IDOT tries to find best rhythm to alleviate congestion most effectively, but release-valve effect diminishing as volume of vehicles in both directions grows

It's just after noon on a recent weekday along the Kennedy Expressway as flashing chevrons activate and a series of 21 gates begins to deploy, shifting available inbound lanes from six to four to give outbound drivers relief for the afternoon and evening rush periods.

During this daily frenzy involving two reversible lanes, a white taxicab speeds past the still-closing gates. Another car also sneaks through.

And seemingly out of nowhere, a black car executed what state traffic engineers dub "the four-lane sweep."

It's a dangerous high-speed maneuver in which a driver in the far right lane veers across the other lanes to reach the reversible lanes, which run on the median of the expressway for 6 miles, from near the Kennedy-Edens junction to Ohio Street.

"We see it every day," Denise Burnes, senior dispatcher at the state's nerve center in Schaumburg for the city's expressway system, said matter-of-factly.

What provokes such risky behavior, for the reward of possibly saving a few minutes? Traffic experts have a theory, and it involves every last vehicle being crammed onto Chicago-area highways.

The reversible lanes, which are the pressure-release valve on the 10-lane Kennedy, used to perform their job well. For years the reversibles were relied upon to essentially generate four lanes of capacity out of two, facilitated by the Illinois Department of Transportation nimbly switching the direction of the express lanes as needed to ease the worst traffic congestion.

But today the Kennedy, which is one of America's busiest highways, is jammed with 260,000 vehicles on an average weekday, IDOT data show. The expressway's "theoretical maximum" is 225,000 to 250,000 vehicles a day, according to IDOT.

Your Getting Around reporter monitored a switch-over Thursday, via live video feeds on large TV screens at the operations and communications center in Schaumburg. It occurred as inbound and outbound traffic on the Kennedy reached a rough equilibrium: 11 minutes from Montrose Avenue to downtown and 12 minutes in the other direction.

Traffic is so heavy over most hours of each day — and it's heavy in both directions — that switching the reversible lanes makes traffic congestion only less worse, not really a lot better, and only in the direction with the two extra lanes, while drivers going the other way feel they are being punished.

"The decision is absolutely getting harder to make," said Steve Travia, chief of traffic operations for IDOT's Chicago region. "There simply is not much benefit to be gained by making the switch when there is equity in the volume of inbound and outbound traffic."

"Trying to be too reactive is actually going to make things worse. I need extra lanes in both directions at this time, so why take it away from one of them and give it to nobody while the reversibles are closed for a half-hour or 40 minutes in order to make the flip?"

The traditional inbound commute in the morning still has a strong edge over the number of vehicles traveling outbound, traffic-count data show.

But the already vibrant reverse commute has grown even stronger in the wake of the Great Recession, and the afternoon rush period is lasting longer, officials said.

The Tribune analyzed traffic numbers from random days this fall. At 7 a.m. Sept. 20, for example, more than 10,000 vehicles were headed inbound on the Kennedy, while about 6,500 were traveling outbound.

But from 4 to 8 p.m., it was a statistical dead heat between outbound and inbound traffic levels. Inbound traffic, mainly reverse-commuters, had a small numerical edge — amounting to a few additional cars per lane per minute — in three out of the five hourly periods.

IDOT changes the direction of the Kennedy reversibles at least two times a day. On Mondays through Thursdays, the flip from inbound to outbound occurs sometime from 11:30 a.m. to 1:30 p.m., based on traffic conditions. The window for the flip back to inbound is from 11 p.m. to 1 a.m.

On Fridays, the flip from inbound to outbound occurs a little later, from 12:30 p.m. to 2:30 p.m. to accommodate a longer period of heavy inbound traffic.

IDOT also often makes an additional switch Fridays — outbound to inbound about 6 p.m., and back to outbound from 8 to 9 p.m., before reverting to inbound from 11 p.m. to 1 a.m.

The 6 p.m. flip is an effort to ease the logjam of drivers headed downtown to restaurants, theaters and other events, while also helping reverse-commuters who live in Chicago and work in the suburbs, officials said.

CHICAGO

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