The eternal argument on speed limits has resurfaced on Twitter. The binary solution is: a) lower speed limits, or b) redesign roadways. This is a false dichotomy, to which I answer yes! Ultimately, the solution is to redesign roads (and motor vehicles) so as to physically enforce posted speed limits. But in the meanwhile, speed limits that are posted too high for urban areas (and with speeds that alway exceed that, because the road was designed for a higher speed than is posted) should be reduced.
There are two types of speed: posted speed, on the speed limit sign, and design speed, the speed that the road was designed for. Design speeds have traditionally been much higher than posted speeds, at least 10 mph higher, and often more, because the traffic engineer’s value system says that we must always protect drivers from their errors by providing a road that is safer at higher speeds. This is highway design thinking, applied to city streets, and is always inappropriate outside freeways and rural roads (and maybe even there). Protecting other users of the road (walkers and bicyclists) does not traditionally figure into this at all.
As a starting point, local or residential streets should be 20 mph maximum, collector streets 30 mph maximum, and arterial streets 40 mph maximum. These are maximums, more than is appropriate for many roads. 40 mph may never be appropriate in an urban area. Of course most arterial streets are stroads, roads designed for higher speeds but then knee-capped my multiple driveways and intersections. These roads should never have been built that way, or allowed to evolve that way, and must be radically changed.
Existing posted speed limits for the city are available.
It should be noted that most research indicates that the majority of fatality and severe injury crashes are caused by people egregiously exceeding speed limits, by 10 mph or more. It is not unusual for speed surveys, and the rare law enforcement, to record a few drivers exceeding freeways speeds on surface streets. Roadway design, along with lower speed limits, probably does little to change the behavior of egregious speeders, and those are better addressed through automated enforcement.
The City of Sacramento has a number of complete streets or road reconstruction projects underway or planned. Two significant ones are Northgate Blvd and Stockton Blvd. Stockton is on the city’s high injury corridor Vision Zero plan, Northgate is not.
The city has been through several cycles of planning for Broadway and Stockton Blvd. The current plan is the Stockton Blvd Plan – Community Working Version. Though public concerns about motor vehicle speed have been a recurring theme, the city plans to address this by reducing travel lanes and planting trees. They do not intend to reduce the posted speed limit. In fact, speed limit is hardly mentioned in any of the documents. In fact, design speed is never mentioned. The city is pretending that posted speed limits have nothing to do with roadway design. The city is not willing to share with the public its intended design speeds.
The posted speed limits on Broadway and Stockton are 35 mph and, south of Lemon Hill, 40 mph. Broadway and Stockton are ‘other principal arterial’ in the state functional classification system, one step below freeway. And much of Stockton’s current design is very freeway-like. Given the intensity of uses along both Broadway and Stockton, posted speed limits of 30 mph would be appropriate. Instead, the city intends to maintain 35 mph and 40 mph for the redesigned road. This will ensure that they remain stroads rather than streets.
Northgate Blvd is not on the city’s high injury corridor Vision Zero Plan, but was identified because it is a road with intensive local use in a disinvested community. The planning effort for Northgate is in an earlier stage. An existing conditions report, appendices, and initial community outreach are available. These reports document that posted speeds are mostly 40 mph, with a small section 45 mph. Recorded speeds are not that far off from posted speeds. but then again, the 40 mph speed is above what one would normally find in an urban area. Northgate is a ‘other principal arterial’, one step below a freeway. Parts of Northgate are have freeway-like designs, but most of it is more like a simple stroad.
Though public concerns about motor vehicle speed have been a recurring theme, the city plans to address this by narrowing travel lanes and planting trees. I participated in the initial workshop on Northgate, and I and others asked whether the posted speed limit would be reduced. The answer was no. But it is early enough in the planning process that this could be changed by public pressure. Another online workshop was scheduled for yesterday (I was unable to participate), and an in-person open house will be October 22 (Saturday, October 22 from 11:30am-1:30pm at Garden Valley Elementary School).
The city’s standard answer to questions about reducing speed limits is that they cannot be changed, because of the 85% rule (not a law, but guidance by Caltrans and courts), but this is incorrect. When a street is reconstructed, whether complete streets or other, the city can design for and set whatever speed limit it wants. It is as though a new street is being constructed. But the city doesn’t want to see it that way.
I think to redesign a road without seriously considering a reduction of the posted speed limit, as well as the design speed, is throwing money down the toilet. These projects will probably be in place for 30 years. 30 years of less than ideal design, 30 years of less than a fully functional and livable street, 30 years of failure to take climate change seriously, 30 years of unnecessarily high fatalities and severe injuries.
Research on the effects of reducing posted speed limits are mixed. Some have indicated a significant impact, particularly at the higher end of the speed range (over 35 mph), and others indicating no significant change. Though even one life saved by a lower posted speed limit is worthwhile to me, it also points out that the ultimate solution to speeding is not just posted speed limits, or enforcement of those, but also roadway redesign. As I said, both!
Law enforcement of speed limits has been well documented as a tool of harassment and oppression of people of color and low income, so I am not in favor of in-person enforcement. Automated enforcement can easily manage speeds and particularly egregious speeders.
Streetsblog: Vision Zero Cities: How to Fix Our Most Dangerous Roads
Streetsblog: STUDY: 20 Is Plenty — But Signs Alone Don’t Always Get Drivers to Slow Down
NACTO City Limits: Setting Safe Speed Limits on Urban Streets