Stop and Go

Traffic signals play a vital role in managing transportation, but have you ever thought about how that management works or how intersections are designed? 

In this episode of Taken with Transportation, we talk with SFMTA Senior Traffic Engineer Bryant Woo, Traffic Signal Electrician Dennis Verhalen and Transit Signal Supervisors Ferdinand Lumbad and John Affolter about how San Francisco intersections, from the most complex to the simple, function and about maintaining traffic signals. They help us understand how the work they do keeps the city moving.

Transcript

MELISSA CULROSS, HOST: It all seemed so simple when we learned about it as kids. Red means stop. Green means go. Look both ways when you cross the street. But managing traffic flow safely is a lot more complicated.

BRYANT WOO, SFMTA SENIOR TRAFFIC ENGINEER: We try and balance the competing needs of, uh, pedestrians, transit and the vehicles.

MELISSA: Welcome to TAKEN WITH TRANSPORTATION, the San Francisco Municipal Transportation Agency’s official podcast. I’m your host, Melissa Culross, and today we’re taking a look at how traffic signals work and intersections are managed. To begin, we catch up with SFMTA Senior Traffic Engineer Bryant Woo in the Chinatown neighborhood near Nob Hill.
 
 MELISSA: So we’re standing here at the intersection of Powell and Washington, and you have told me this is a really complex intersection. To me, a person who doesn’t know anything about this, it just looks like streets. What makes it so complex?
 
 BRYANT: It’s got literally everything. We’re half a block from Gordon J. Lau Elementary. We’re two blocks away from Firehouse Two. We have two, uh, intersecting cable car routes, as well as proximity to the Central Subway station, the typography, and the fact that we have approximately a-hundred-and-thirty-year-old antiques for the cable car… This signal is the most complex, in my opinion, in the city.

MELISSA: As activity swirls around us, Woo offers up more detail.
  
 BRYANT: This is the intersection of two opposing one-way streets. So Washington flows, uh, westbound east of the intersection, and it flows eastbound west of the intersection. And obviously, you don’t want head-on collisions to occur at the same time, and so those two opposing directions never see a green light at the same time. Next, we have traffic on Powell Street getting the green light. In this case, both directions can go at the same time because no turns are allowed because you have two opposing one-way streets. Next, we have a pedestrian signal at the south light of the intersection. Uh, you can see it counting down. Count-down signals are commonplace now, but folks have to remember that 15-20 years ago, they were a rare sight. And, uh, we have a group of tourists. They’re family, and they’re holding a map. When that cable car comes through, they are gonna be detected by sensors located in the trackway. And, uh, when they’re coming through, depending on the direction that they’re going, they will receive a white, vertical traffic light that will be separate from the red, yellow, green, signals for exclusively the cable car to be able to move.

MELISSA: If that sounds like a lot to manage, well, it is. And Woo tells us that some users of an intersection get priority.
 
 BRYANT: A common misconception that folks have, understandably so, is that all they see, in general are the red, yellow and green lights. But in reality, the biggest importance to us is serving the pedestrians. Especially, we’re mindful of the fact of the proximity to the school, as well as this particular area has a high concentration of seniors living in the area. We, uh, give more time than the, uh, national standard for these, uh, older pedestrians to cross, or younger children who are being escorted by their, uh, parents or caretakers. And we also include in this signal what we call accessible pedestrian signals. That’s for the individuals who are visually impaired. We also include as a part of our projects, features like curb ramps for individuals who are in wheelchairs or some other type of assisted walking device, whether it be a, uh, walker or a cane. These are all features as we include as part of our signal projects. So, first order of business is serving the pedestrians.
 
 MELISSA: Are cars held here longer than other intersections or longer than normal? I’m standing here watching the traffic; it doesn’t seem like they’re waiting terribly long.
 
 BRYANT: So, everything’s a balance, and that’s what makes the intersection complex and the job challenging. And so, we try and balance the competing needs of, uh, pedestrians, transit and the vehicles. And so, one of the ways that we can do that is by including transit-only lanes or special means of detecting transit vehicles. So that we don’t give the time to those vehicles unless they’re actually there and actually need it. 
 
 MELISSA: What are some examples of, sort of, more simple intersections, and what is the experience like at some of those for people who live and, and move around the city?
 
 BRYANT: The simplest, uh, intersection would be, uh, a four-legged intersection out, for example, in the Outer Richmond or in the Outer Sunset districts? It goes red, yellow, green in one direction, and it does red, yellow, green in the other direction. And coupled with that, we have pedestrian signals to go with it. Even that one, uh, we have, uh, little tricks here and there that we do to make things as safe as possible. So, we do things like, uh, what’s called a leading pedestrian interval. This is where the pedestrian sees a walk light for about three or four seconds before the green light turns on. That gives the pedestrian the opportunity to establish themselves in the intersection and give them the right of way and, uh, help reduce pedestrian-related collision. Other things that we do is we coordinate the signals, uh, to help control traffic speeds. Uh, we reduce speeding, and, uh, traffic moves more uniformly, which also reduces collisions. So, even in a basic intersection out in the Outer Richmond or the Outer Sunset, there’s a lot of thinking that goes behind it. 
 
 MELISSA: When we say “complex,” do we necessarily mean “dangerous?”
 
 BRYANT: No. First order of business (is) to make sure that everybody can move through the intersection safely. And when the situation calls for it, we separate the movement of pedestrians from the movement of transit, from the movement of bikes, from the movement of cars. So, just a block down, for example, over on Stockton Street, uh, we have what we call a pedestrian scramble, where all the pedestrians crossing go at the same time. And then after that happens, then the vehicles get to go. So, first order of business, of course, is safety for all users, and we may have to separate the movements, if we have to. But we always make sure everybody can travel through safely.

MELISSA: Traffic engineering starts with collecting good data, Woo says, including the number of vehicles and pedestrians that pass through an area and where they’re going, emergency vehicle considerations and…for cable cars, in particular…any operating limitations. Then the SFMTA collaborates with other city agencies such as Public Works, the Public Utilities Commission and the Mayor’s Office of Disability…as well as stakeholders like Walk SF.
 
 BRYANT: All of those play a part in designing a signal. So, we have issues with accessibility. We have issues with drainage; hence the Public Utilities Commission is involved. They’re also responsible for streetlights, so we have the streetlights. And then Public Works does, uh, some of the electrical engineering design, as well as the civil engineering design for things like the curb ramps, the grading of the intersection. And oftentimes they also manage the construction contract. So, it’s all of this collaborative effort that goes into designing and then operating the signal. And that’s often why, much to the chagrin of your everyday citizen, uh, it takes so long to design and construct what would normally look like Christmas tree lights, but it's a lot more complex than that.

MELISSA: Even with safety-focused designs, things do happen sometimes, and traffic signals and poles need to be replaced. That takes us across town to the SFMTA Traffic Signal Shop where electricians and support staff maintain hundreds of traffic signals, communication systems and related hardware. Transit Signal Supervisor Ferdinand Lumbad gives us the lay of the land. 

FERDINAND LUMBAD, TRANSIT SIGNAL SUPERVISOR: A typical day for Traffic Signal Shop is, basically, we…our shift starts at 7 o’clock where all the crew meets together and have their assignments assigned to them. Some of those assignments can be programming a timing change to intersections, installing an APS button…audio pedestrian signals… or installing signals from different locations.

MELISSA: As we walk around the shop, we happen upon a crew member programming an audio pedestrian signal.

SIGNAL ANNOUNCEMENT: Washington. Walk sign is on to cross Washington. Wait to cross Washington at Stockton. Wait.

MELISSA: The crew also handles maintenance requests or complaints from all over the city. Traffic Signal Supervisor John Affolter.

JOHN AFFOLTER, TRANSIT SIGNAL SUPERVISOR: Typically, we, uh, respond to very serious complaints right away. Such as, uh, cabinet knockdowns, electrical cabinets, that is, that control the intersections; traffic signal poles; live electrical wires; stuck intersections; turn-vehicle heads; including pedestrian signals. For obvious reasons, these are all really hazardous situations. Additional complaints that we respond to, uh, that may or may not be as serious, uh, we have dark intersections and short circuits; mast arm signal damage; visor damage; out-of-synchronization. That’s, you know, keeping the greens coordinated so traffic flows freely, and not just for cars but for, uh, trains, streetcars, buses, bicycles, as well.

MELISSA: Affolter describes a few recent incidents in which signal equipment was hit by cars:

JOHN: This one here’s, uh, Golden Gate and Gough. Street light pole with traffic signals on it and lots of signage. Nailed it right in the center of the grill. Knocked the pole down. Fortunately, nobody was hurt. And this one here is Alemany and Farragut. And you can see it looks like scorched earth where they hit the electrical cabinet, knocked it over, and somehow it ignited. And it also caught the, uh, PG&E pole next to it on fire, which burnt the actual service that was providing the power for the intersection. So the intersection went completely dark. And see, uh, the cabinet was stretched out, all the wires got burned.

MELISSA: And Traffic Signal Electrician Dennis Verhalen tells us about the repair work he did earlier this summer after an SUV ran into a traffic signal at 19th and Guerrero Streets in the Mission.

DENNIS VERHALEN, TRAFFIC SIGNAL ELECTRICIAN: This was actually Pride weekend, I believe it was, and it’s just a block away from Dolores Park. The police were actually doing a really good job of kind of keeping people away from it. But myself and the Line Helper, we slung the pole, got it over this skywire here, brought it down and took it apart so that the tow trucks could come in and actually remove the vehicle. Before that even, we’ve gone to the cabinet and made sure that the wires that are feeding the pole are, are all disconnected, so there’s no…any potential for live circuits out there in the field. So this particular one we had to put up a temporary base, which is basically a two-and-a-half-foot diameter concrete base with just a small pole on it, and we’ll put a temporary signal there so that cars and pedestrians have signals until we can get a real pole up.

MELISSA: Back at Powell and Washington Streets, Bryant Woo wraps up our discussion with a little more about transit signal priority.
 
 BRYANT: This particular intersection has cable car detection, but, uh, many of our intersections throughout the city also have both bus and emergency vehicle detection. The city’s Transit First policy directed us to prioritize the movement of transit, bikes and pedestrians. So these, uh, types of detection systems are used, again, to promote transit, uh, reduce travel time, reduce their delay, and we use that same system to reduce the delay of our first responders. You can’t see it. It’s all wireless, and you might see some antennas and equipment mounted, uh, on the signal pole. But, uh, there’s a lot of thought and a lot of work that goes into it, and, uh, you may not realize it until you actually need that type of service.

MELISSA: Thank you for joining us on TAKEN WITH TRANSPORTATION. We’re a production of the San Francisco Municipal Transportation Agency, and you can find the latest episodes at SFMTA.com-slash-Podcast, as well as Apple, Spotify or wherever you listen. I’m Melissa Culross. Be well and travel well.