Flashing Hands And Countdown Timers

Q: I have a question on traffic signals for pedestrians. My understanding is that when a pedestrian comes up to the corner to cross the street and the red hand light is flashing, they are not supposed to start across. I see pedestrians constantly starting to cross when the red hand is lit and the seconds are showing. They seem to think that they are okay to start across as long the seconds are showing. Who is right on this?

A: By a show of hands, how many of you, when you see a pedestrian traffic signal with a countdown timer, look at the remaining seconds, calculate whether you can cross the street that fast, and then make a run for it? You can all put your hands down now.

Before we get into pedestrian signals with countdown timers, let’s do a quick refresh on a traditional pedestrian signal. My apologies in advance for stating the obvious:

• Walking person symbol: You can start crossing the street now.
• Flashing hand symbol: Don’t start crossing the street, but if you’ve already started, go ahead and finish.
• Solid hand symbol: Why are you still in the crosswalk?

This system works reasonably well, except during the flashing hand phase, when pedestrians are tempted to start crossing in hopes that they’ll make it across before the flashing hand turns solid. Sometimes people guess wrong on how much time they have and end up in the middle of the intersection when the lights change.

That’s where countdown pedestrian signals come in. They are designed to, in government language, “help pedestrians make better crossing decisions at signalized intersections.” Based on crash data, they seem to work. Crashes decrease in intersections that switch to countdown signals.

You could argue that traffic engineers just caved to bad behavior. Adding the timer is like saying, “We know they’re going to start crossing the street after they’re supposed to; let’s just add a timer so they know how long they have until they get run over.” However, I prefer to think of it not as bad behavior, but as under-informed behavior.

The length of the “flashing hand” phase of the pedestrian signal is based on a 3.5 feet per second walking pace (a bit over 2 MPH). That’s pretty slow. Someone with a fast walking pace around 4 MPH could conceivably step onto the sidewalk well after the signal switches from “walking person” to “flashing hand” and still cross the street before the 2 MPH walker who started during the “walking person” phase. And that’s exactly what happens.

Unfortunately, when a walker overestimates the distance he can cover before the signal turns to a solid hand, he ends up in the wrong place at the wrong time. Giving the late entry pedestrians a timer lets them know how long they have to finish crossing the street. A gift to the rule-breakers? Maybe. But does it work? Compared to traditional pedestrian signals, those with countdown timers have more pedestrians entering the intersection after the signal switches to the “flashing hand” phase, but less pedestrians remaining in the intersection when the signal reaches the “solid hand” phase.

Even though it’s against the law to enter a crosswalk when the hand is flashing, being in the intersection during that phase does not increase a pedestrian’s risk of getting hit. The danger comes during the “solid hand” phase, when the lights change for the cars. It seems that this piece of traffic engineering has traded an increase in illegal behavior that doesn’t increase pedestrian risk for a decrease in illegal behavior that has the potential of serious consequences.

If that trade doesn’t feel quite right, consider that this isn’t the only place where traffic engineering assumes some road users will break the law. We put guardrails up to prevent speeders and distracted drivers from driving off cliffs. We have traffic signals with a phase where all signals are red, just in case someone tries to make it through the yellow and fails. We’ve added rumble strips to wake up sleepy drivers before the end up in a ditch. Part of traffic engineering is designing systems to minimize the consequences of mistakes and bad judgment.

Let me be clear that I’m not advocating for ignoring traffic laws and assuming the engineers have us covered. But we’ve built a transportation system around humans, who aren’t really that good at identifying and responding to hazards on the road. It makes sense to build in safeguards until the robots take over the driving for us.

On a somewhat related note, it’s been a while since I’ve provided any traffic trivia. Since we’re approaching the holiday season, and all the social events that ensue, let me equip you with a bit of information so you can impress the guests at your next gathering with your traffic knowledge. The orangish-red color that lights up the hand in a pedestrian signal has a name: It’s called Portland orange.