The Cass Street bridge is slated to be turned back into a one-way route on Saturday, but it won’t necessarily stay that way.

The Illinois Department of Transportation is conducting a study to determine the feasibility of making the bridge a permanent two-way route.

The study already was underway when IDOT agreed to make the bridge and streets leading up to it a temporary two-way route while the Jefferson Street bridge was shut down. The temporary two-way was done in May at the insistence of Mayor Bob O’Dekirk, local legislators and business leaders who wanted better downtown access as Jefferson Street bridge repairs stretched far beyond the original two-month schedule.

“It seems to have worked out,” Joliet Public Works Director Greg Ruddy said. “It kept access to the downtown going.”

The Jefferson Street bridge was reopened on Monday after being closed for nearly 20 months.

On Saturday, the Cass Street bridge will be closed from 6 a.m. to 3 p.m. as IDOT changes road striping, signs and signals that had been set up to create the two-way route from Hickory Street on the west side of the bridge to Joliet Street downtown.

The bridge then will reopen as a one-way route heading west.

IDOT had been hesitant to make the bridge a two-way out of concerns that a temporary change in the road pattern would create confusion and accidents.

During the nearly 10 months that the bridge was closed there were two accidents on Cass between Hickory and Joliet streets, according to Joliet police.

There were no injuries in either accident.

The most recent accident on Dec. 30 involved a vehicle going west in the converted eastbound lane on Cass Street. In early August, a vehicle in the westbound lane on Cass Street appeared to make too wide a turn at the Joliet Street intersection and hit a vehicle stopped at the light in the eastbound lane, police said.

What impact those accidents and other factors have on the IDOT study won’t be known for several months yet.

“We’re looking to complete that study sometime later this summer,” IDOT spokeswoman Maria Castaneda said.

The study involves both Cass Street, which carries U.S. 30 west of downtown, and Jefferson Street, which carries U.S. 30 east into downtown.

“They have to look at it as a dual route,” Castaneda said. “It’s not just Cass. They have to look at Jefferson, which is one-way eastbound.”

Complaints about downtown driving often turn to the number of one-way routes.

But they do serve a purpose in carrying higher volumes of traffic, Ruddy said.

Without opposite lanes of traffic, there are fewer turns at intersections and fewer phases at traffic signals.

“Most of the one-way streets downtown – the major streets – are state routes,” Ruddy said. “In order to increase capacity on those streets, they use what is called the one-way couplet. One street goes one way, and another goes the other way.”