There are many features on our streets that often go unnoticed when we’re driving, walking, biking, or taking transit. Roadway markings for construction or bike lanes, slabs of concrete in the roadway (or in St. Louis’ case, steel plates), and many other features are often just things most of us whiz past when we’re getting from point A to point B. 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. I’m talking about slip lanes. You may not have heard of slip lanes, or even one of their other names (channelized right-hand turn lane, Australian right) but there are dozens of them throughout the St. Louis region and other cities across the country.
What are slip lanes? Why do they exist?
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. Most commonly seen when coming on or off an interstate or a high-speed, multi-lane road (Kingshighway, Lindbergh, etc), the common justification for the implementation of slip lanes is to reduce vehicle congestion. 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 slip lanes have one massive flaw: they are extremely dangerous for people using non-motorized means of transportation (walking, biking, etc). Slip lanes allow people who drive to make an unimpeded right-hand turn, instead of a full stop and turn done at most 4-way intersections. The slip lane design is another example of how our streets have become more about prioritizing the speed and efficiency of motor vehicles over the safety of more vulnerable roadway users, like people who walk or bike. Not only do slip lanes encourage fast vehicle speeds, but they also make the crossing distance longer for people walking, in some cases (most slip lanes along Chouteau for instance) adding 25 extra feet for pedestrians to cross.
Federal Highway Administration – Crash Modification Factor for Corner Radius, Right-Turn Speed, and Prediction of Pedestrian Crashes at Signalized Intersections
Moving Forward without Slip Lanes
So what can we do about slip lanes? Are there effective strategies to make slip lanes safer for non-vehicular transportation modes? One strategy that we are seeing federal agencies like the Federal Highway Administration recommend is the “Australian Right.” The Austrian Right is still a slip lane, except cars enter the right-hand turn lane at a tighter angle compared to a normal slip lane. Australian Rights are being implemented at a greater frequency in the United States and may even be implemented at the intersection of Chambers & W. Florissant as a part of the W. Florissant Great Street Project. Cities have also implemented raised crosswalks within slip lanes to slow cars down through the slip lane and increase visibility for people walking. The city of Boulder, Colorado has slip lanes with raised pedestrian crossings throughout the city with signage notifying drivers to slow down and watch for pedestrian traffic.
There is one effective solution to make slip lanes safer for people walking, biking, and driving: GET RID OF THEM! 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. Instead, we should reprioritize slip lane space for things like bus stops, outdoor seating/gathering places, green space, and other uses. There are countless examples of cities already doing this, and I personally believe that most slip lanes in St. Louis could be transformed into people-centered spaces that promote placemaking, art, and nature. I’ve taken a few examples of slip lanes across St. Louis City and redesigned them, check out my very amateur sketches below!