Forrest Soule and Alexander Tang

Systematic Safety Assignment: Protected Intersections

August 5, 2016

Protected intersections get their name from the curbs and medians that separate and protect bicyclists and pedestrians from motor vehicles. They are a safer alternative to conventional intersection design where bike lanes will suddenly end at the junction, or in cases where roads with sharrows intersect.

Issues with Conventional Intersection Design

In a conventional, or old, intersection, bicyclists are at risk of being right-hooked. A right-hook incident is when a bicyclist is riding on the right side of the road, and a car is turning right. The car does not notice the cyclist and turns right, cutting them off, or running them over. Additionally, a bicyclist turning left at a conventional intersection must take control of a vehicle’s travel lane and dangerously navigate through an open swathe of pavement surrounded by moving vehicles. This can lead to serious collisions between bicyclists and cars.

Protected Intersections are the Solution

In a protected intersection, the problems of the right hook and the dangerous left turn are solved. To prevent the right hook, often times the right turning lane gets its own green light while the bike signal stays red. Other times, when both lights are green simultaneously, protective measures are in place. Vehicle stop lines are set back from bicycle stop lines. The cars have clear view of the bicyclists before the light turns green.

Additionally, this setback means bicyclists are usually out of the way before the car even turns the corner. The corner safety islands force the car to enter the street at an angle closer to 90 degrees, allowing a better view of incoming bicyclists. In some cases the bike signal will turn green a few seconds before the car signal, letting bicyclists clear the area before cars make their right turn. Lastly, a blinking yield light reminds drivers that a bicyclist might be coming up on their right.

In order to turn left, a bicyclist must cross the road and go into the bicycle waiting area and then cross again. This ensures that throughout their entire turn, they are completely separated from fast moving vehicles.

Systematic Safety Principles

Systematic safety, or sustainable safety, is a concept used in roadway design in which the actual design of the road causes people to drive safely. In the Netherlands, their entire road network is built with this in mind. Instead of utilizing this strategy, The United States relies on signage and laws to prevent reckless driving. Unfortunately, signs and laws are not always adhered to.

According to SWOV, the Institute for Road Safety Research in the Netherlands,  Systematic Safety takes into account the functionality of roads and attempts to reduce the severity of collisions through equality of speed, direction, and mass. Systematic safety also encourages the predictability of road usage and driver behaviour through self-explanatory design and allows drivers to analyze and adapt to what is ahead.

Protected intersections equate the speed and mass of road users by separating the cars and bicyclists. Both modes of transport end up travelling among the same types of vehicles instead of mixing. If a bike collides with a bike, the severity of collision will be lower than a bike colliding with a car. Both the cars and bicyclists have their own space. These intersections encourage predictably of road users with the use of separate traffic signals and space for cars, bicyclists, and pedestrians.

Implementation

The Netherlands use protected intersections wherever possible. When there is not enough room for a complete protected intersection, crossing islands can be reduced in size. When there still is not enough space, the crossing island can be eliminated altogether, essentially becoming an apex ramp for bicyclists.