Alternate Idea for Passing on Missouri’s Highways

Trying to pass a slower moving vehicle on a two-lane highway can be both frustrating and dangerous. In order to help make Missouri highways safer and reduce the number of fatalities and disabling injuries that occur each year, MoDOT has embraced the concept of an alternate four-lane design on certain routes.

An alternate four-lane consists of an additional lane added to one side of a conventional two-lane highway to provide motorists an opportunity to pass another vehicle without having to find gaps in the on-coming traffic. The passing lane alternates between the north and southbound lanes giving motorists from both directions ample opportunity to pass.

MoDOT installed its first alternate four-lane in November 2005 on Route 37 between Monett and Cassville in District 7 and others are now underway.

Compared to the two-lane passing lane, the alternate four-lane is safer because motorists will never have to drive into a lane with oncoming traffic and it has a paved shoulder and rumble stripe. Plus, the passing lane configuration is much cheaper than constructing four-lane roads.

“These alternating passing lanes will help us reduce the number of fatalities and disabling injuries on our roadways,” said Eileen Rackers, state Traffic engineer. “Many sections where we are installing these alternating passing lanes have a history of motorists making the choice to pass when it is not safe to do so, which can lead to head-on collisions. Head-on collisions are one of the most deadly types of traffic crashes.”

Since the installation of the alternating passing lanes, head-on collisions have decreased on this roadway section. Dave Taylor, Traffic operating engineer in District 7, says they will review the segment again next summer since the roadway has a higher traffic volume then.

Other alternate four-lane projects have sprung up in Missouri since the installation of the ones in the Southwest District. District 9 recently completed installation of their own alternating passing lane on Nov. 21 on an 11-mile stretch extending from Houston to Licking in Texas County. Districts 5 and 8 will install a stretch of alternating passing lane on Route 5 south of Camdenton in the summer of 2010.