dimanche 31 juillet 2011

Bicycling in Holland –Signalized Intersection Practices with cycle tracks

Part of the Bicycling in Holland project. http://wiki.coe.neu.edu/groups/nl2011transpo/wiki/bd54f/Bicycling_Facilities_in_Holland.html

By Kate Petak, Kourus Monsef, and Ian Trout

Although they are relatively new in the US, bicycle signals have been used for many years in The Netherlands. The purpose of bicycle signals is to provide safety, directness, comfort, and ease of use for cyclists. Bike signals increase safety because they alert drivers that there are cyclists in the vicinity and reduce conflict by using methods such as advance green, which allows bicycles to move independently of cars. Bike signals provide directness in both time and distance. Delays can be limited by maximizing right of way and minimizing wait time. The alignment of the signal should follow the most direct route across the intersection whenever possible. Bike signals increase the comfort and ease of use for cyclists because the signal heads are placed in easily seen locations on the right side of the cycle track so that cyclists don't have to reference car signals.

According to the CROW design manual for bicycle traffic, “collisions between cyclists and cars are the most significant cause of serious traffic accidents involving cyclist. Over half of these accidents occur at intersections within built-up areas (58%) and of these particularly at intersections with 50 km/h roads (95%).” In order to provide safety and comfort to the large number of cyclists in The Netherlands, the CROW manual endorses the use of traffic control systems (TCS) for intersections where between 10,000 and 30,000 pcu/day need to be handled. The CROW manual ranks TCS second to roundabouts in terms of bicycle safety. Intersection practices involving TCS commonly consist of a signal, any possible advance detection such as inductive loops, microwave detectors, and a bicycle push button.(Figures 9 and 10) The safety features of a bicycle signal include less conflict with vehicles, advance green lights, advanced stop lines, and protected left turns. They are important in reducing the number and severity of bike-car accidents by minimizing the speed difference between vehicles and cyclists at intersections. TCS's can also significantly impede the flow of cyclists. The CROW manual states that “an average waiting time of less than 15 seconds is good, while one of more than 20 seconds is poor.” The maximum waiting time at a bike signal inside the built-up area is 90 seconds; outside the built-up area it is 100 seconds. A shorter cycle length (less than 90 seconds) is more beneficial for cyclists than the generally accepted time of 120 seconds for auto traffic. Extended green is not currently used for cyclists.

The CROW manual states that road management authorities should develop TCS policy with regards to priority. For example, “a basic principle that can be applied is that main cycle routes have right of way at intersections inside the built-up area. It is also possible to indicate maximum values for waiting times or cycle times.” Comparing this with US practices, the AAHSTO guidelines state that cyclists can have extended green cycles and that the signal should “provide sufficient time for a rolling cyclist who enters at the end of the green interval to clear the intersection before traffic on a crossing approach receives a green indication”. Average waiting time at a bike signal was not stated. Advantages for bikes and bike safety is that the minimum green time for cyclists is longer than the minimum green time for cars and the all-red phase at intersections involving cyclists is increased to the longest interval used in local practice. Detection used in the US includes not only inductive loops and microwave detectors, but also video and radar technologies.

In The Netherlands, bike signals can be located at the same height as a vehicle signal head, at a cyclists eye level, or in both places. (Figure 1) When placed at eye level, a smaller size signal display is used. Usually bike signal heads were measured to be 8-in (20-cm) in diameter and lower signal heads are 3 ft (1-m) high with a 3 in (7.5-cm) diameter face. The signals can have either solid lenses or blackened lenses with bike pictograms.
Figure 1: bike pictogram signal (Amsterdam, Netherlands)

 Figure 2: solid lenses bike signal (Rijswijk,  Netherlands)

There are no flashing indications on the signal heads except at night. Advanced green phases for bicycles are sometimes used simultaneously with a red phase for right-turning vehicles.
The bike signals are located on the near side of the intersection, whereas pedestrian signals are located in the middle and far sides of the intersection.

Additional signal heads that are used may have directional arrows in red, yellow and green indications. Figure 3 shows this type of bike signal which was taken at a T-intersection at Buitenhofdreef and Griegstraat in Delft, Netherlands.

Figure 3: Bike signal using left directional arrows @ location #9

 Figure 4: Straight arrow bike signal

Bicycle signal detection at traffic signals is used to alert the signal controller of bicycle crossing demand on a particular approach. Bicycle detection occurs either through loop detection, push button, or a combination of both. (Figure 5) Induction loops are placed at the signal, in advance, and for queue detection; sometimes, microwave detectors, placed on the signal post above the signal head, are used in conjunction with the loops. (Figure 8)
Figure 5: signal with queue and loop detection in Houten 

Figure 6: signal with loop detection and microwave detection @ location #4

Figure 7: intersection of Julianalaan and Oostpoorweg @ location #3 

Figure 8: intersection of Oostpoortweg and the A13 entrance ramp @ location #4    

The microwave detector was used only at a few intersections that we travelled through, such as Julianalaan at Oostpoortweg and Oostpoortweg

Signal design practice and loop detector layout varies in the Netherlands (as it does in the U.S.) Most of the intersections have a single loop detector located just in front of the stop bar. (Figure 6) Some have two loops right in front of the stop bar, located just a couple of feet apart from each other. Advance detection loops are placed well ahead of the intersection (about 80 feet) and will trigger the light to turn green so that the cyclist does not have to stop. Theo Muller of TU Delft indicated that the loops aren’t used for extension in many instances.

The current standard of “push” buttons consists of a yellow post with a red light on it. (Figure 10) The red light comes on when a bicycle has been detected via the loop detector or by the cyclist manually activating it. The post is located at a height that is easily accessible for most cyclists to comfortably reach while remaining on the bike. The loop detector is calibrated to detect bikes so that in most cases the cyclist does not have to manually activate the signal. The old push buttons are small round buttons that, when pushed, would cause a light to come on at the bottom of the box; however, many of these had lights that were no longer operational. (Figure 9)
Figure 9: old push button @ Westlandseweg and Papsouwselaan

Figure 10: new push button with light @ Westlandseweg and Provincialweg location #5

Countdown Timers
There are two main types of countdown indications given to cyclists. They consist of LED lights that either form numbers that count down or form a ring of dots that gradually disappear, much like a clock. (Figure 11) These indications are placed adjacent to the light for easy visibility. The clock signal is the preferred countdown method because it has a greater compliance rate, as the numbered countdown can deter cyclists from waiting the designated cycle length. Both the countdown and the clock have variable speeds: the countdown can skip numbers if the car cycle is shorter than expected and the clock signal can tick down slowly or quickly, also depending on the car cycle. A special bicycle warning signal is given for bus and tram crossings. (Figure 12)
Figure 11: Bike signal with a countdown timer attached @location #10.

Figure 12: Warning devices activated by buses or trams approaching @ location #7.

Conflicts usually occur at intersections where there are different types of travelers crossing each other’s path. One of the important factors in order to reduce these conflicts is the design of an intersection along with proper cycle lengths for each signal. Good design will indicate to those that are approaching the intersection what their action should be and who will yield to whom. Bicyclist and pedestrians are at a disadvantage regarding conflict points due to their lesser size and visibility. The CROW manual has the following guidelines: conflicts are to be avoided, but sub-conflicts between motorists and bicyclists is acceptable so long as:
  • There are not a lot of right turning trucks
  • The cycle track is one way in the direction of the ongoing through traffic.
  • The intensity of motorized traffic turning is not greater than 150 pcu/h.

In comparison, NACTO suggested that in order to resolve right turn conflict, a car signal with a no right turn arrow is put in, and “an active display to help emphasize this restriction is recommended”.
One of the ways in order to reduce the conflicts between motorized vehicles and bicyclists is having an advanced stop line for the cyclist. This provides cyclists time to clear the intersection and increased visibility. The following figures demonstrate an example of this application. In this location, the traffic signal and stop bar for vehicular traffic is placed 40 ft behind the bike signal and stop bar. Also in Figure 13, there is a warning sign for motorists making a right turn to watch out for pedestrians and bicyclists.
Figure 13: Vehicle traffic signal indicating caution for cyclist and pedestrian traffic @ location #1.

Figure 14: The bike stop bar and the vehicle Traffic signal and stop bar in the background

Left turn Design
Left turns can be made in a variety of ways. They can be made with a left turn signal as in Figure 3, an immediate turn from one cycle track to another, or a segmented turn by crossing one street and then turning and crossing the other street. By using green waves, cyclists can often make the left segmented turn without having to stop. There is an example at the intersection of Westlandseweg and Buitenhofdreef in Delft. (Figure 16)
Figure 15: direct left turn signal with left turn stacking lane @ location #3.

            Figure 16: segmented left turn @ location #6.

The system can be set up for recall, but the recall setting varies among intersections and time of day. The recall setting is on if the red light comes on automatically, as the system is effectively pushing the button for cyclists whether or not any cyclists are present. At night, some intersections, for example Julianalaan at Oostpoortweg, have flashing yellow lights for cars and bicycles at all approaches.  
This functions as an all way yield. In this situation, the bike signal cannot be activated and the pedestrian signal is turned off altogether. The flashing yellow policy puts a lot of trust in the relationship between drivers, cyclists, and pedestrians to be aware of each other and yield.

Bike signals give independence to cyclists so that they do not need to refer to car signals at intersections. Bike signals increase safety and compliance and are easy to use. In cities, a series of signals can be set up such that there is a green wave. For example, on Raadhuisstraat in Amsterdam the green wave is set to 18 kilometers per hour so that cyclists can easily
cross multiple roads without stopping. The video can be seen here:
An advantage of having bike signals operating independently of car signals is that the phasing can be altered in order to favor cyclists. An example of this is the "twice green" traffic light regimes. In The Netherlands, there is concern about bicycle delay at signalized intersections. According to Fietsbalans, although average delay has decreased in recent years, only 40 percent of this improvement is due to improvement in the signal timing. According to Bo Boormans, director and traffic control expert of DTV consultants, having a "twice green" phase is the most obvious way to reduce waiting time for cyclists. This means that the cyclists will have two green lights per cycle. For more information go to:

Measurements and observations
The stop line is typically located halfway in between the signal pole and the push button. The distance between the signal pole and the push button ranges from 5 to 10 feet, though there are exceptions such as in Figure 3. At Westlandseweg and Provincialweg, (Location 5) the stop line for cyclists was about 40 feet ahead of the stop line for cars. In addition, conflict between cyclists and right turning cars was eliminated by providing approximately 11 seconds of green time to cyclists getting to the median, then providing green time to right turning cars. The phasing varied depending on the detection of right turning traffic. The green time for cyclists at this intersection varied from 5 seconds to 15 seconds. In comparison, the green time for cyclists in Davis, CA, as stated in the NACTO guidelines, ranges from 12 seconds to 25 seconds.

Typical Applications:

Left turn bike lane and a straight bike lane @ location#2. Weaving of cars is permitted as seen in 2nd photo, creating a sense of insecurity and deteriorating the sense of safety.

Another photo of the left turn bike signal @ location #3

Transit priority TCS coupled with a bike signal @ Provincialeweg and A. Flemingln

bike signal @ Haantje and Beatrixlaan

intersection where weaving is a potential conflict at location 11

bus activated warning device

bike signal just outside Houten with a countdown signal on the lower level signal head

Google map of Delft, NL with the locations of photographs numbered and corresponding   locations.


CROW Design Manual for Bicycle Traffic. English Language Edition. 2007.

Hendriks, Ron. "Twice Green Almost Always Feasible". 2010. Fietsberaad. 23 Jul 2011. http://www.fietsberaad.nl/index.cfm?lang=en&section=Kennisbank&mode=detail&repository=Twice+green+almost+always+feasible

Fietsberaad. "Green Wave Raadhuisstraat". 5 May 2009. Fietsberaad. 23 Jul 2011. http://www.youtube.com/watch?v=xVuRjQgoomU&feature=related

Peter Koonce blog: Microwave Detector for Bicycle Traffic in Delft. 12 July 2011. http://koonceportland.blogspot.com/2011/07/microwave-detector-for-bicycle-traffic.html

To continue reading other chapters of the Bicycling in Holland project, go to: http://wiki.coe.neu.edu/groups/nl2011transpo/wiki/bd54f/Bicycling_Facilities_in_Holland.html

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