Q: I’ve encountered two types of pedestrian-activated crossings; one that flashes yellow and one that flashes red. But both, more often than not, are treated the same by motorists. This raises the possibility of motorists colliding when one stops and the other doesn’t at a flashing red crossing. Shouldn’t there be more consistency to prevent crashes?
A: I’m a big fan of predictability and consistency when it comes to driving. When you know what to expect from other road users, and from the stuff we build to manage traffic, it’s safer for everyone. But maybe the pedestrian-activated signals you described actually are consistent, at least with the law. And to the extent that they’re different it’s not increasing rear-end crashes; not on a measurable scale, anyway.
The Manual on Uniform Traffic Control Devices (MUTCD) is the Bible for traffic signs, lights, and markings. You know how when you drive from city to city and state to state the stop signs are still red octagons? It’s mainly because of this manual. In it, you’ll find two kinds of pedestrian-activated signals.
The kind with the red lights is called a Pedestrian Hybrid Beacon (PHB), formerly known as a High-intensity Activated crossWalK or HAWK. And yes, I know I capitalized some wrong letters in that name, but that’s the textual gymnastics required to get that acronym. PHBs generally get installed on high-traffic roads with lots of pedestrians where there isn’t justification to install a traditional traffic signal, like where there’s a low-traffic cross street. Deciding to install a PHB involves charts and math, but the simplified version is, if the combination of vehicles and pedestrian crossings per hour is high enough, you might need a PHB.
The flashing yellow pedestrian signal is called a Rectangular Rapid Flashing Beacon (RRFB). I’m not sure you could come up with a better name to precisely describe its physical qualities while simultaneously telling you zero about its purpose. An RRFB is intended to “provide supplemental emphasis” at crosswalks, essentially telling drivers, “Hey! Watch out for a person in the crosswalk here!” RRFBs don’t need to meet the requirements of a traffic study, so you might find them on roads with lower traffic volumes than a PHB.
Both the PHB and the RRFB function in a manner consistent with how we use flashing signals elsewhere for traffic management. A flashing red works like a stop sign, and a flashing yellow is a caution signal. Yes, the two kinds of pedestrian-activated signals are different, but if we follow the laws for red and yellow flashing signals, we’ll do just fine.
But do PHBs increase crashes? I reviewed crashes over the last five years for a one-mile stretch of high-traffic road that included 18 intersections – four with traditional traffic signals, four with PHBs, and the rest with no signals. In my non-scientific and small sample size study, the intersections with signals averaged 15 crashes. Intersections without signals averaged 1.3 crashes. Before you conclude that traffic signals cause crashes, remember, we put the signals at the busy intersections. Intersections with PHBs averaged one crash. That would suggest that PHBs reduce overall crashes, especially considering that PHBs get installed at intersections with more vehicle and pedestrian traffic, compared to their neighboring intersections.
And while we’re on the topic of pedestrians, I’ll note that the good news about the 21 percent decrease in traffic fatalities over the past couple of years for people in vehicles doesn’t apply so much to pedestrians (seven percent decrease). Drivers, we have some work to do to make sure people walking stay safe, so be alert out there.
If you have a traffic related question you would like to ask, click here.