By Clare Creedon
Introduction
Bicycling through intersections has the highest risk for accidents. Generally, in the United States, bicycle lanes will end at this converging point increasing a cyclist’s vulnerability. Although, sometimes, markings will continue through the intersection, a protective design fails. A design focused on systematic safety should control all traffic so there is no conflict. A common Dutch facility that applies systematic safety is the protected intersection. This type of intersection reduces impacts of human error and is self-enforcing. The protected intersection incorporates the following elements of systematic safety: separation, speed control, restrictiveness, predictability, and simplicity.
Background
Figure 1: Protected Intersection (Cycle Track meets Cycle Track)
Protected intersections separate bicyclists and pedestrians from traffic as they approach the intersection. Once cyclists and pedestrians meet the intersection, design is intended to fend off cars at vulnerable areas. This type of intersection focuses on turning points since that’s where cars are least likely to see crossers. The main features of this design are corner refuge islands, forward stop bars for cyclists, set back crosswalks for cyclists and pedestrians, bicycle traffic signals, and pedestrian platforms. These simple elements will permit users to make coherent actions at intersections, minimize conflict, and allow traffic to run efficiently.
Corner Island
Figure 2: Car and bike paths divert at corner island to meet at a tee
The corner island is a round, mounted barrier that allows cyclists to securely wait deeper into the intersection. Corner islands create a space to separate cyclists from car traffic. They extend outwards to push cars away from the sidewalk and are angled to slow down turning cars. Primarily, the placing of a corner island diverts cars at a ninety degree angle to maximize drivers’ visibility at crossings as they meet cyclists at a tee (see Figure 2). This feature restricts a vehicle’s most direct route so that velocities are controlled without the need for speed limit signs. In this case, the road is self-enforcing for speed checks.
Forward Stop Bar
Figure 3: Separation between cars & bikes/pedestrians
The forward stop bar is where cyclists wait when their light is red. It is strategically placed further in the intersection than where cars wait for their light. Figure 3 demonstrates how visible cyclists are to drivers at the intersection. While also giving cyclists an advancement (versus cars) in the intersection, a forward stop bar will reduce the distance cyclists must cross.
Figure 4: Two Stage Left Turn
The forward stop is very important in assisting cyclists turning left via a two-phase turn. You can see in Figure 4, the light green line and yellow numbers showing the the parts to this type of turn. This will give the rider an opportunity to cross one street at a time; hence, they make one decision at a time. Fewer decisions at a time highlights the simplicity that is a two-phase turn. By restricting the cyclist’s ability to merge left, cyclists are given a low-stress experience by crossing two sides of the street at a time with protection from other vehicles.
Set Back Ped/Bike Crossings
Figure 5: Set Back Crossing for Pedestrians and Cyclists
Rather than have a bike lane run straight through the intersection, bike lanes (and pedestrian crossings) are bent outwards to increase the space between bikes or pedestrians and moving cars. This separation of space corresponds with additional time to react to potential conflict. The set back is usually 15-20 ft or the length of a car. This set back also leaves a space for cars to wait, not in the middle of the intersection, while people are crossings to eliminate congestion.
In addition, bike and pedestrian crossings along with their road markings enable motorists to predict what may happen at these points. Bike crossings have dotted white lines and pedestrian crossings include “zebra stripes”. Sometimes the bike crossings are red as well to further alert drivers of the zone. A consistent pattern on the roads, such as symbolic markings and coloring, tells drivers how they should act in certain areas.
Bike Signal Phasing
To make sure pedestrian and bicycle traffic run smoothly while avoiding conflict, bike signaling is very important. This must sync with the car signaling for best efficiency and safety. The safest scenario is to have the bicycle light green while cars have red. Leading bicycle interval is an alternative that starts a bicycle green light a few seconds before a car’s green light. Bike signal phasing is key for cyclists making left turns (2-phase). The simplicity of crossing one side of the street at a time is possible with an optimized bicycle signaling.
Car traffic signals at the intersection can also maintain low speeds if desired through timing. This engineered control can optimize safety with slack time in signaling. Systematic safety calls for preparing for the worst such as those who speed through the yellow light. A signaling system that allots more time between a car red and a bike green is forgiving to those who may not be driving as safely as expected. This is a buffer for the unexpected.
Pedestrian Platform
Figure 6: Stages of a Pedestrian Crossing
One feature not mentioned in the articles I’ve read about protected intersections is the pedestrian platform. This designated area adds to the “simple” and “separated” components of systematic safety. This raised area creates a barrier between pedestrians and faster moving traffic. Figure 6 exhibits the stages of a pedestrian crossing. The red circles denote pedestrian platforms. A pedestrian waits for an appropriate time to cross the cycle track from the sidewalk and finds refuge at this platform. Next, the pedestrian waits until the right time to cross the vehicular traffic until coming to the next pedestrian platform. The median is variable and not always there as a place of refuge. The pedestrian platform is between roads for two forms of moving traffic so pedestrians are separated and protected.
Based off of my measurements, pedestrian platforms range from 7.2 ft. to 15.4 ft. These dimensions may vary, but given a platform approximately this size will provide a comfortable waiting space for pedestrians about to cross the road. This platform provides pedestrians with more time to make less decisions when crossing the road. Instead of looking both ways to cross traffic going both ways or multiple modes of traffic, a pedestrian can simply approach one type of road at a time.
On average, people walk 4.5 ft/s, and signals give 7 seconds for cross walkers. Waiting platforms allow pedestrians to get closer to the other side of the road and have a smaller need for lengthy crossing time. This will reduce inefficient delays with the rest of the signaling.
Something I noticed was that when the distance is shorter across cycle tracks, the zebra crossing markings may not appear. Figure 1 shows such an example in which there are no crossing markings because the distance from sidewalk to pedestrian platform is fairly short at 5.9 ft. Crossing markings are not always necessary since pedestrians have a straightaway view down the cycle track to see if traffic is coming. Regardless, people want to cross as few as lanes at a time in which the pedestrian platform helps achieve.
Typical Example
Figure 7 – Cycle Track meets Cycle Track
Click here: Typical Protected Intersection
A typical protected intersection has cycle tracks meeting cycle tracks. This the safest way to integrate mixed modes of traffic at an intersection as cyclists are physically separated from traffic unless crossing the road. The junction of Sir Winston Churchillaan and Burgemeester Elsenlaan (Rijswijk) in Figure 7 exemplifies a situation where users of the road can understand simply what to do. Dashed lines in the middle guide turning drivers to their chosen lane. Red pavement signifies bicycle paths. Elephant feet point to cyclist crossing areas, while typical lines are for pedestrians. And yield markings called “shark teeth” determine who must yield to who.
Cyclist turning right will easily be able to do so without a wait because the cycle. No conflict should occur on this separated bike path, since pedestrians must yield when entering the crosswalk. Meanwhile, cyclists continuing straight can wait at the forward stop, out of anyone else’s way, until it is their turn via signal. If they cannot make the second light, they may wait in the center of the road at the median. Any cyclists that wants to turn left will wait will do so safely in the aforementioned two-phase turn.
Although a tram passes through the intersection, its straight path down the middle does not affect cyclists since tracks are perpendicular enough to crossing wheels while the signalized intersection will prevent any collision. Cycle tracks run parallel to the road far enough to avoid collision of cars and to give people enough room for comfort or low stress riding.
Cycle track + Bike Lane
Figure 8 – Bike Lane converts to Cycle Track
A variation of a protected intersection has a cycle track that converts into a bike lane after the intersection. Figure 8 shows this special case of a protected intersection which occurs in the north to south direction. This is not ideal since bikes are not completely separated from car traffic. The bike lane is bent at sharp angles (see yellow lines) to control speed of cyclists as they approach pedestrian crossings. The bend happens before the pedestrian crossing area to “forgive” any speeding cyclists and forces them to slow down with its design.
In addition, this bike lane still applies systematic safety with its “predictability”. Bike lanes have red asphalt and border vehicular traffic with dashed lines. This tells drivers to remain in their respected lanes and to keep caution of cyclists. The consistency of red on the road is a recognizable design so that road users know how they should behave with a mixed traffic, particularly bicyclists.
Figure 9 – Car vs. Bike Turn Separation
Every other bicycle path is the typical cycle track to cycle track conversion before and after the intersection. I did notice in the other direction of this mentioned special case (south to north), the cycle tracks that meets a cycle track ends up changing to a bicycle lane about 260 feet from the intersection. This local road, Pr. Margriets/Doctor HJ van Mooklaan, has a smaller volume of cars than Sir Winston Churchillaan and less space to allocate to cycle tracks. This is why a bike lane is the decided facility for bicycles along these roads. Sir Winston Churchillaan is an arterial road, so cars are trying to get direct, quick access to a destination. Cycle tracks are much more necessary on such a heavily trafficked and faster road like Sir Winston Churchillaan to meet the comfort and safety needs of cyclists.
Semi-Protected Pocket Lane
Figure 10 – Semi Protected Pocket Lane
Streetview: semi-protected pocket lane at intersection
A special case of the protected intersection includes a semi-protected pocket lane as seen at the intersection of arterial roads, De Heemstraat/Parallelweg and Hoefkade (The Hague). Rather than having a completely protected route, cyclists going west to east use a semi-protected bike lane that later converts to a cycle track. The bicycle lane lies on the left of the right turning lane. Meanwhile, a concrete median separates the bicycle lane with the straight or left turning vehicular lane (see Figure 10). This means that cyclists have only one threat to be aware of, the right-only lane which shouldn’t affect them. This is safe if all road users stay on their defined path. Once in the intersection, the bike lane drops the red coloring and protection is limited to traffic signal phasing. This bike facility keeps traffic flowing smoothly so that bicycles don’t have to wait for cars turning left and vice versa. This decreases queueing, so there are no cars waiting to turn left behind the cyclists going straight. The pocket lane also prevents “right hook” conflicts, where a car would turn right and hit a cyclist going straight. The streetview link above shows the beginning of the semi-protected pocket lane. Cars that want to get in the right only lane must cross over the bike lane before it become semi-protected. Again, this is not the most ideal situation for a protected intersection, but when space is sometimes limited, it is a good solution.
By observing how people use this intersection, I’ve seen speeding and bicycles crossing the street without a green light. I can also assume bicycles are turning right on red which poses more threats than if there were a physical separation. To prevent potential accident, the design can be adjusted to improve signal timing. Cycle tracks will allow bicycles to turn right with little friction and more protection. Corner refuge islands will control drivers’ turns moreover as they are guided with visibility. Nonexistent forward bicycle stops and pushed out crossing will decrease risk of conflict on all sides of the intersection.
Figure 11 – Semi-Protected Pocket Lane
The variation of a protected intersection with bike lanes is comparable to a similarly designed L Street in Washington D.C. Figure 11 shows a pocket lane that is semi-protected because of bollards placed between both through lanes. They provide a physical barrier and separate the bikes from the cars continuing straight. Drivers in the left lane will slowly down as they meet the intersection due to a ninety degree angled turn, and drivers on the right side have already committed to going straight. This design restricts both lanes of traffic so that they do not interfere with cyclists riding through the intersection. The pocket lane is is colored green to make drivers aware of its presence. A bike box lies horizontally in front of all other waiting traffic to provide cyclists with a head start as well as allow more cyclists to get through the intersection. Cars must wait behind the row of cyclists at the light. This restrictiveness will slow cars down while increasing the flow of cyclists as they must regain momentum.
Conclusion
All of the above complement each other as a systematically structured safe design for intersection fluidity. Instead of waiting for something to fail and then fixing it, we should be utilizing solutions we have for one problem wherever that issue may exist again. Part of systematic safety requires a certain amount of dependence on design in order to control commuters. While every intersection has its own space restraints and variables such as volume or capacity, the typical protected intersection should include the corner safety island, forward stop, set back pedestrian/bike cross walks, bike signal phasing, and a pedestrian platform.