Week 1: Traffic Calming in SF and LA

Welcome back everyone to my blog!

This week I looked at Vision Zero projects and policies of two major US cities, San Francisco and Los Angeles. They taught me the design principles and changes to intersections that must be taken.

There are shared guiding principles of every Vision Zero initiative:

• People will make mistakes on the road.
• The consequences of these mistakes should not be death or severe injury.
• Reducing vehicle speed is fundamental to safer streets.

Now that we have some more insight, let’s dig deeper into the source of the problem.

There are a small portion of roadways that disproportionately account for collisions, in LA a 6% portion of roadway accounts for 70% of pedestrian deaths and severe injuries. While SF has 13% of its roadways account for 75% of severe and fatal injuries. These have occurred on what are called ‘stroads’.

A stroad is a phrase coined to describe a roadway that combines the characteristics of a street and a road but fails to effectively serve either function. A road is supposed to quickly move cars to and from a location. While a street functions as the heart of commerce within a city with low-speed traffic, lots of pedestrians, and many stores people can easily access. Stroads typically feature wide lanes, high speeds, and limited pedestrian and cyclist infrastructure. However they also have multiple access points between businesses and fast-flowing traffic, where pedestrians have the least protection. This has, unfortunately, facilitated deadly results, with almost 60% of all pedestrian deaths in the US during 2022 occurring on stroads.

That is why many cities have to decide how to treat their roadways, either as roads or streets. To make a stroad into a road it would mean reducing access points so traffic moves quicker while giving a safe space for pedestrians and cyclists. To make a stroad into a street it would require slowing traffic and prioritizing public and active transit, while also focusing on building to fill gaps and expand existing structures.

Now that we know the problem, what can we do? The need to reduce car speed at intersections as one of the main goals of vision zero projects, many traffic calming measures have been proposed to suit this goal. Shared intersection changes include: slip lane closures, leading pedestrian intervals, pedestrian refuge islands, and daylighting.

• Getting rid of slip lanes, a separate right turn at intersections for unimpeded vehicular movement. Many cars travel at high speeds to quickly join traffic and many times there is inappropriate line of sight for drivers to see pedestrians. Instead the two cities have put in pedestrian bulb outs in place of slip lanes, having cars stay with straight bound traffic and installing large radii circles to slow down cars as they turn. I have shown an example (not in LA or SF) below where the right turn was made much sharper and required drivers to slow down, while previously they may not have even had to tap the brakes.

Before

After

• Leading pedestrian intervals give pedestrians 3-7 second head start before a green light for cars, which lets them be more visible to cars and has been shown to reduce collisions by almost 60%.

• Pedestrian refuge islands are a median that is intended to help protect pedestrians who are crossing a road. It reduces the length at which a pedestrian is in danger of being hit by cars and by installing these islands they can reduce pedestrian collisions by up to 56%.

• Daylighting simply means getting rid of objects, such as parked cars or trees, 20-25 ft before an intersection to enhance driver visibility. As well as restricting lane width at the intersection and giving that space to the sidewalk to reduce the length pedestrians need to cross the road.

The following are some unique intersection projects related to the individual city that I wanted to highlight as they are a good first step in creating safer crossings for cyclists and pedestrians at intersections:

SF Vision Zero – Left turn calming at Montgomery St & Broadway: The left turn safety treatments consist of installing waist-high vertical delineator posts, small rubber speed bumps, and paint to create enhanced center lane lines and painted safety zones to encourage slower, wider left turns and increase drivers’ awareness of other road users. In 2019, 40% of traffic deaths in San Francisco were caused when drivers made left turns and didn’t see the person in the crosswalk, until it was too late. By adding safety treatments to intersections that encourage drivers to take left turns more slowly. Slower speeds give more time for drivers to avoid collisions and can also result in fewer fatalities in the worst instances.

LA Vision Zero – High intensity activated crosswalk (HAWK) at Western Avenue: They are lights activated by a pedestrian pushing a button. HAWK signals are used to notify oncoming motorists to stop with a series of red and yellow lights at intersections at crossings that are spaced far apart from intersections to be convenient for pedestrians. These are best used at high-speed conditions or wide arterials that give faster service to pedestrians and less delay to motorists than traffic lights.

I wanted to talk about all of this to show there are a diverse set of plans that can be created to enhance pedestrian safety. These actions, however, have happened at a small scale, due to budget constrictions for both cities’ department of transportation. They could only do ‘quick build projects’, intervention for one intersection at a time. That is why when we take a look at the bigger picture, it seems more grim. Los Angeles has actually seen a slight increase in pedestrian deaths and San Francisco has seen no change in pedestrian deaths. But this doesn’t mean Vision Zero is a failure, a more optimistic view is that the projects that were completed by the city helped to stave off even greater pedestrian deaths. As post-pandemic conditions have affected cities across the country, pedestrian deaths rose by 13% even as overall travel declined. Next week I want to show some more lasting, and wide scaling projects that can be seen in Fremont through its Vision Zero policy. As well as learn what an actual traffic engineer has to say on the effectiveness of certain vision zero features and the design principles which successful projects are based upon.

Tune in next week to learn more!