The Great Highway Road Survey
By: Wai Yip Tung
Tags: Traffic, Smart Cities, Great Highway

Since the Great Highway was closed to traffic from 2020, it has become a prominent outdoor spot. People immediately discovered this new oceanfront promenade. Each day, it is visited by thousands of walkers, runners, and bikers. Yet many people want it to return to the old way. They complained about the closure, making apocalyptic remarks about the impact.

To understand the impact of Great Highway closure, I have gone out to survey on the ground information. I have visited multiple locations multiple times. First, I have made street level observations. I have made 9 video recordings at various main roads in the morning and evening commute hours. Next, I have done driving tests during commute hours. The course goes around 19th Ave, Sloat, Sunset, Golden Gate Park and then back to 19th Ave. I have made two loops in the morning and two loops in the afternoon in both directions. All trips have detailed GPS recording for analysis. It is clear that despite the closure, traffic is light in the entire west side of San Francisco. There is no traffic disruption to speak of.

Street Videos

I have went to multiple locations in Sunset to survey the traffic during commute hours. They are recorded in the videos below, each is a few minutes long. My observation is that traffic varies from light to moderate. Traffic was especially light on the Great Highway going to Lincoln. It is not hard to find long stretch of time when there was not a single car in any of the four lanes. In all cases, traffic flows freely at full speed. This is very much unlike the more populated areas in San Francisco.

Great Highway at 5pm

Driving Test

Next are the driving tests. I have thought that driving during commute hours will be a painful exercise. But in reality, it was quite pleasant. The roads west of 19th Ave are all open and free from traffic. The only traffic I’ve encountered are all on 19th Ave or to its east. The short stretch of Stanyan next to Golden Gate park stands out as the worst on the whole course.

Driving Test Route

Sunset Boulevard is the designated alternative route to the Great Highway. This was already the case before the pandemic. According to SFMTA, the Great Highway was closed 27 times a year on average due to sand accumulation. The detour to Sunset Boulevard is a familiar exercise to drivers. As it turns out, the six lane boulevard has plenty of capacity to handle the combined traffic. The average speed on Sunset Boulevard tops all other major roads at 22.8 mph. This average speed includes the time spent stopping at red light. 22.8 mph is about as fast as you can go in any city streets of San Francisco. Compare this to 16.3 mph average on Geary Boulevard.

There is an even easier way to monitor traffic than driving it. You can do it at home by opening Google Map with real time traffic information. You will see the same picture, there is no traffic to the west of 19th Ave. This can be confirmed by multiple sources.

The function of Great Highway?

It may be surprising that losing a four lane highway did not cause any traffic disruption. But it is not surprising when you pay attention to the geography. The map below highlights the area served by each main road. On the far west side of the city next to the ocean, Great Highway serves the smallest area in the western half of outer Richmond in the light blue box. Note that Great Highway does not even serve the outer Sunset because there is no access from there. In comparison, 19th Ave serves a much larger area in San Francisco. There are more residents and more business along 19th Ave. Moreover, it is also the state highway 1, carrying traffic between Golden Gate bridge and 280. Sunset Boulevard is somewhere in between. Given the smallest service area, it is not surprising that traffic volume is rather low by San Francisco standard.

Service Area of 19th Ave/Sunset Blvd/Great Highway

When we think about transportation planning, people tend to want to revert to the status quo. The conventional wisdom says closing a four lane Great Highway will cause major traffic disruption. There is a problem that need to be addressed.

On the other hand, it has been more than one year since the Great Highway was closed. The conventional wisdom turns out to be an illusion. All evidence shows that traffic is doing just fine without it. The new status quo is the Great Highway no longer carries any traffic. The question we should consider is, were the Great Highway not built, is there a demonstrated demand for it now? When all of highway 1 traffic is carried by just six lanes, is there a justification for ten lanes of roads to handle the light traffic in just Outer Sunset and Outer Richmond?

Many people are not aware that the Great Highway south of Sloat is already scheduled to be closed due to long term soil erosion. When that happens, the utility of the Great Highway will be further eroded.

The Great Restoration

When the Loma Prieta damaged the Embarcadero Freeway, people suddenly saw a new opportunity to use the space. Today, the waterfront is restored into a beautiful promenade. Just as is the case on the bay side, nature has intervened on the ocean side. An extended closure started off due to sand accumulation has given us a new opportunity to re-envision the oceanfront. The case of restoring the Great Highway into open space should be a much easier call to make. Unlike the Embarcadero Freeway which carries a lot of downtown traffic, Great Highway’s function is already subsumed by Sunset Boulevard, which is a lot more reliable without the regular problem of sand accumulation. We should seize this opportunity to restore the Great Highway both north and south of Sloat into open space!