The Trouble With Slip Lanes

"There is one roadway design feature that is becoming a point of contention in many communities and you’ve probably driven or walked through one at least once," writes Sam McCrory of the slip lane. Also known as channelized right-hand turn lanes, "Slip lanes are separate turn lanes that allow cars to make a right-hand turn without fully stopping for a red light at an intersection," McCrory explains.

If people driving are allowed to make an unimpeded right-hand turn, engineers believe that congestion will decrease. Slip lanes are also implemented for other reasons, like vehicle safety and consideration for larger vehicles. Slip lanes do help reduce t-bone style vehicle crashes, which are typically more dangerous to people driving; and because of their wide turning angle, slip lanes are more favorable for larger vehicles like semis, emergency vehicles, and delivery trucks to make turns in urban areas.

But there's one significant catch, writes McCrory. Slip lanes "are extremely dangerous for people using non-motorized means of transportation (walking, biking, etc)." According to the article, "In many scenarios slip lanes are completely useless and only cause confusion and negative safety outcomes for people using them. A simple way to increase safety is simply to stop implementing them."

McCrory recommends repurposing slip lane space "for things like bus stops, outdoor seating/gathering places, green space, and other uses," illustrating several potential examples at St. Louis intersections where slip lanes could serve more people-friendly purposes.