Another major city has lowered urban speed limits in an effort to make its streets safer. As of Monday, Boston’s default speed limit dropped from 30 miles per hour to 25, about the same as going from 50 km/h down to 40. The move is part of Boston Mayor Martin Walsh’s Vision Zero commitment.
Vision Zero is traffic safety philosophy that acknowledges the inevitability of human error, and focusses on designing systems so that common mistakes don’t result in major injuries and deaths. The city of Boston’s announcement explains how the lower limit fits in to its Vision Zero mission:
Legislative efforts, like lowering the speed limit, combined with enhanced street design, education and enforcement policies work together to create a street system and standard of behavior [sic] that dramatically reduces the consequences of everyday mistakes. Mistakes can and will happen, but they should not be deadly or lead to serious, life-altering injury.
Right now, Halifax is perfectly poised to consider a similar move. Our new 10-year transportation plan (Integrated Mobility Plan, or IMP) is in its final stages, and with it, we will be asking city staff for the next decade to embrace the idea that our streets are meant for people of all ages and abilities, using all modes of transportation. We will be reclassifying roads to better reflect their actual use, and further using modern street design tools to make them safer and more efficient for all. The IMP promises to bring the reign of vehicle traffic flow as the priority in our cost-benefit analyses to an end. Moving cars is no longer the end game. In fact, the goal is to move less of them.
I can think of few simpler and more useful ways to express this new value system than to follow the lead of cities like Boston, New York, and Montreal, and reset our default urban speed limits.
Let’s draw a line around our urban streets, the areas where large amounts of pedestrians, cyclists, buses and cars mix, and collectively state the need to slow down.
There are parts of Halifax and Dartmouth where walking and cycling are the primary ways people commute. It’s time that the laws of our streets reflected this mixed mode reality.
We need to have a conversation about this: We need to talk about how certain streets, even within our urban core, are designed for speeds above 50 km/h, while others are designed for speeds well below. We need to determine once and for all which is worse: to perpetuate the idea that it’s safe to drive 50 km/h everywhere in the city, or to have to work towards actually building our streets to match our new values.
We need to talk about the fact that changing blanket regulations like speed limits in isolation won’t necessarily change driver behaviour. And so we also need to talk about how to bring our street design in line with our values. The law doesn’t work in isolation, but the law should reflect our collective ideal. And right now, our blanket limit of 50 km/h is too high for safe mixing of modes that we have decided time and again we want on our streets.
The current speed limits in Nova Scotia have been set using something called the engineering method, which relies heavily on a measurement of 85th percentile speed. “That’s basically the speed at which 85 per cent of your traffic is going at or below,” provincial traffic authority Mike Crofts explained to me in June when I last wrote about speed limits. “The thinking behind that, and this has been studied to death actually, is that 85 per cent of your drivers drive at a safe and prudent speed. They’re reasonable drivers. That 85th percentile speed is often a key determinant in setting the speed limits.”
The 85th percentile method simply measures what drivers do. That means 15 per cent of drivers go faster. The premise is that people are reasonable and know what’s safe — that we can feel when our speed is getting dangerously fast.
My question about the 85th percentile method is: What if average people driving cars are wrong? I mean, I trust my instincts while driving will kick in to protect me and my car, but will they kick in in time to protect a teenager crossing the street or a cyclist beside me?
What if the idea of “safe and prudent” from a person seated comfortably in a moving metal box is different than the idea of “safe and prudent” from the average pedestrian? What if, in the decades of using the engineering method to determine speed limits, we have failed to update our own premises, like what exactly constitutes “safe and prudent”? How many traffic injuries and deaths do we accept at “safe and prudent” speeds?
The traffic safety capital of the world, Sweden, has long since abandoned the engineering method of speed limit setting. The originators of Vision Zero way back in 1997 use a “safe systems” approach, where the goal of injury minimization is key. For a deeper look at the very interesting thinking behind Vision Zero, check out this interview with Swedish traffic safety strategist Matts-Åke Belin.
We also use 85th percentile speed to determine if we have speeding problems on streets. Maybe, instead of measuring vehicle speeds to determine where there’s a speeding problem, we should instead be interviewing pedestrians and cyclists. They are much better poised to have a sense of what is “safe and prudent” on a mixed-mode street, after all.
Of course, Halifax cannot single-handedly reset the default speed limit. We need approval from Mike Croft, the provincial traffic authority, who has traditionally said no to municipalities looking for speed limit changes on isolated streets.
But with the IMP, Halifax is setting a new direction for how we move people around the city, and we are committing to changing our streets to better match our values. We will have centrally organized, comprehensive design goals for our streets. A reduced default speed limit as part of the IMP could stand a chance of being approved by our provincial traffic authority.
At the very least, the IMP should be starting this important discussion.