The Drive: Escape lanes help motorists merge

For motorists heading north out of downtown Minneapolis on Interstate 94, overhead signs before ramps for the West Broadway/Washington Avenue and Dowling Avenue interchanges inform them that the far right lane is designated "exit only."

That means all traffic in the far right lane is supposed to get off the freeway at the ramp because lanes marked "exit only" typically end at the off ramp. The warning sign is meant to give motorists continuing past the exit point or lane drop ample time to move one lane over.

So why, in some cases, do lanes marked "exit only" extend several hundred feet past the off ramp, then taper traffic into the general purpose lanes?

The short paved areas adjacent to an exit lane are called recovery lanes by transportation departments in several other states and escape lanes by the Minnesota Department of Transportation. The purpose of the auxiliary lanes is to give drivers who have just entered the freeway enough time and space to merge into traffic, and to give drivers who find themselves unintentionally about to exit the freeway room to maneuver back onto the through-traffic lanes, said Darwin Yasis, a geometrics engineer for MnDOT.

Escape lanes have been getting more attention over the past decade as the metro area's traffic volume has increased, Yasis said. They are most common in areas such as on eastbound I-94 in downtown Minneapolis, where the closely spaced on and off ramps at Riverside and Cedar avenues and 5th Street can make it hard for drivers to merge during peak travel periods.

"In cases where you have high traffic volumes, where drivers have difficulty merging, we provide those escape lanes," Yasis said. In areas where MnDOT cannot add additional travel lanes, "providing escape lanes provides us with the extra capacity to merge into mainline traffic."

According to MnDOT's policy, escape lanes are placed at exits or a major fork in the road where merging or exiting can be difficult. Conditions that warrant building an escape lane include interchanges with two consecutive loops in the direction of travel or when ramps are spaced a half-mile apart or less. They also can be placed in areas with high traffic volume and when weaving conditions warrant them.

Yasis said most drivers tend to merge early and usually don't need to use escape lanes. But it is OK to do so if necessary.

Escape lanes are not marked with signs because the "exit only" directive means exactly that.

"We would not want drivers to be encouraged to use them if they don't need to," he said. "When you don't have a congested mainline, drivers generally merge early and you don't end up utilizing the whole merge area with the additional escape lane," Yasis said. "That is the typical driver behavior. 'Exit only' signs are for people in advance of the exit, to let them know that they are already in an exit lane and they are not supposed to use it as a get-ahead lane."

Escape lanes are not as common today as they once were. Back in the 1970s and early 1980s, MnDOT's policy was to put in an escape lane any time a lane was labeled as "exit only" so as not to trap drivers, Yasis said. That's why escape lanes still exist at the Washington and Dowling exits, even though those interchanges no longer meet the current criteria, which were instituted in 2001.