3 different intersection treatments compared
As nearly half of all bicycle-car crashes happen at intersections, there is a very clear need for interventions that could provide cyclists with extra protection. The new study used a bicycling simulator that replicates traffic conditions to evaluate the safety of 3 different intersection treatments – a mixing zone, bicycle signals, and the bike box.
- Mixing zone – Coming into the intersection, the bike lane is replaced by different lane markings that indicate bicycles will be sharing a lane with cars looking to cross the bike lane area to make a right turn.
- A bicycle signal – This is a special traffic light for bicycles. When the bicycle signal turns green, the cyclist is free to cross the intersection, when it’s red, the cyclist has to stop and wait.
- Bike box – A box is painted on the ground at the front of the intersection with a bike symbol inside. This box spans the whole width of the road which allows cyclists to go past the cars and stop in front of them to wait. It gives cyclists a head start through the intersection and makes them more visible to motorists.
The researchers put 40 subjects through multiple scenarios in the simulator for each of the 3 intersection treatments. The simulator consisted of a stationary bicycle in front of a large screen displaying the road, vehicles, and all other relevant information. The researchers charted the paths the subjects took for analysis. The subjects also had their eye movements tracked, their stress levels measured by galvanic skin response, and they were also surveyed after.
The bike box is the safest
Out of all 3 studied treatments, the study showed that the “bike box” provided the best balance between increased safety and readiness to respond to dangerous situations.
“Time-space measurements showed that the mixing-zone treatment correlated with the most unpredictable riding behaviours. With a bicycle signal, analysis of the participants’ eye movements revealed a lower rate of detecting a potential conflict vehicle. The bike box proved the most effective treatment for encouraging safe riding habits while also providing enhanced safety for bicyclists at signalized intersections,” said co-author, David Hurwitz, a transportation engineering professor at Oregon State.
The mixing zone creates discomfort
The study found that the mixing zone may be viable in certain types of intersections. Unfortunately, it created the most discomfort among the subjects but also made them the most careful.
“The mixing zone has potential if we are limited by the available right of way for other design alternatives. Positioning data indicate cyclists are willing to merge with the traffic but the sporadic and unpredictable riding habits associated with a mixing zone may expose bicyclists to higher risk,” said lead author Logan Scott-Deeter.
The bicycle signal was the most comfortable
The bicycle signal appeared to be the least useful. It created a false sense of security to some extent. The subjects felt the most comfortable with this treatment but they also paid the least attention to their surroundings.
“The eye-tracking data clearly showed reduced vigilance in searching for potential conflicts at the intersections. Thus, we’d recommend installing bicycle signals only when there is a clear need for them,” said Hurwitz.
Have you encountered any of these three intersection treatments? Which one do you prefer?