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Pedestrian Actuated Signals on Sidepaths

Sidepath at Signal

Sidepath at Signal by VeloTraffic, on Flickr

Anytime a cyclist is riding on an off-street path parallel to a roadway (also called a sidepath), they are legally obligated to follow all of the rules and regulations that we expect pedestrians to follow, including following the walk and don’t walk signals.  Modern technology permits traffic engineers to create complex traffic signal timing plans designed to optimize the efficiency of the intersection.  Unfortunately, some of the techniques engineers use to govern the timing of the pedestrian signals can result in a frustrating experience for cyclists.

When an engineer designs a signal phasing plan, they guarantee that any time a walk signal is displayed, the signal will stay green long enough to allow the pedestrian to safely cross the street. In the olden days (before my time) when signal cycles followed a fixed timing pattern regardless of traffic conditions, engineers just programmed the signals so that every green phase was long enough for a pedestrian to cross the street.  Since engineers generally used a conservative 4.0 ft/s walking speed to calculate the minimum amount of time a signal had to be green to allow a pedestrian to cross, engineers often had to allocate a lot more green time than was required based on the number of vehicles present – even if pedestrians were relatively rare.

The solution to this problem was to introduce the pedestrian activated walk signal, a feature used on virtually all new traffic signals installed these days.   This feature provides engineers with the flexibility needed to optimize the amount of time given to each direction of traffic based on real-time traffic conditions without having to worry about how long it would take a pedestrian to cross the street.  At these signals, the don’t walk signals are always activated in all directions unless a pedestrian pushes the button indicating the direction they’d like to cross. After the button has been pushed, the pedestrian will be shown a walk signal the next time vehicles traveling in the same direction are given a green signal.

Pedestrian actuated signals can either be a benefit or an inconvenience for cyclists.  Consider, for example, the following hypothetical situation:

A cyclist is traveling on a sidepath parallel to a relatively low volume roadway.  As the cyclist approaches a major intersection with a major roadway, he stops at the don’t walk signal and pushes the button indicating that he wants to cross the major roadway.  During this time of day when traffic on the low volume roadway is rare, the signal is designed to react immediately when a vehicle is detected on the low-volume side street or the pedestrian button is pushed.  The signal governing the major roadway immediately turns yellow, and then red.  Within 12 seconds of pushing the pedestrian button, the cyclist is given a walk signal and is permitted to cross the major roadway.

In this hypothetical example, the pedestrian actuated signal provides a real benefit to the cyclist. On average, the cyclist will experience less delay waiting for a walk signal than if the signal followed a fixed timing plan.  However, consider the following example:

A cyclist is traveling on an off-street path parallel to a high-volume roadway during the PM rush hour.  She reaches the intersection two seconds after the vehicles traveling parallel to her in the same direction are given a green signal.  Unfortunately, she had not pushed the pedestrian button before the start of the phase when the walk signal would normally be given, so the don’t walk signal is still displayed.  She knows from previous experience with this intersection that the traffic signal will be green in the direction she wants to go for quite a while – plenty of time for her to quickly ride across the intersection.  However, the don’t walk signal remains displayed, regardless of how fiercely she repeatedly pushes the button.

These types of signals guarantee that there is no such thing as “catching a green light” for a cyclist on a sidepath.  For cyclists that arrive at a signal during the phase when the walk signal would be activated (had someone pushed the button), this can be a frustrating or confusing experience. Some cyclists will wait through the entire cycle for the walk signal, but they won’t be happy about it.  Other cyclists may assume the walk signal is broken and try to cross anyway. Others will recognize that they didn’t arrive soon enough to activate the walk signal, but they will cross anyway because they are confidant that they’ll be able to do so safely.  For yet other cyclists, this inconvenience will be enough of a deterrent that they will choose to ride in the roadway with motorists (where they can “catch the green lights.”)

For most cyclists, this will be a relatively minor inconvenience.  However, engineers and planners should recognize that this inconvenience increases based on the number of signals cyclists encounter along a roadway, and the likelihood that they will arrive during a green phase.

4 comments to Pedestrian Actuated Signals on Sidepaths

  • Melanie

    I’ve been frustrated by this very thing lots of times, but never really thought of the engineering implications behind it. I usually end up just crossing without a signal- either in the road or in the crosswalk, but it always makes me slow down and do a double take to make sure there isn’t a reason I didn’t get a signal. It will be awesome when there are signals designated for cars, pedestrians AND bicycles.

  • Shaun

    It seems like they should re-write the logic so if someone shows up on a green light and pushes the button, with enough time left in the signal to make a safe crossing, the “walk” signal should change

  • @Shaun – you’re right. It would be simple to introduce this logic into the signal timing plans. I think part of the reason that nobody does this is that there aren’t very many times when a pedestrian would push the button and there would still be enough time to cross (since engineers have to assume that all pedestrians are very slow, making pedestrian crossing times very long). But again, this is an example of how cyclists are sometimes poorly served by this system (since cyclists don’t require nearly as much time as pedestrians).

  • Thank you for pointing out this disadvantage to bike or ped actuated signals – I’d like to add that it is illegal to cross against the walk signal, even if it is perfectly safe.

    In addition, actuated signals are often inaccessible during the 1-4 months a year (depending on the winter) they are blocked by snowbanks, effectively illegalizing non-motorized traffic.

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