Reducing Speed and the Cost of Mistakes
By reducing the speed on our streets we can make mistakes less costly
The other day I was riding my e-bike home from getting cat food at Woofmeow and as I was making a right turn from Grove Street onto 6th Street I made a mistake and accelerated too fast while turning. Because of this, my turn was pretty wide and I found myself closer to the double yellow lines in the middle of the street than I would have liked. A passing driver yelled at me out of her window, “Be careful!”, and I shouted back an apology. I didn’t feel like I had lost control or anything, but I recognized that I should have let off of the throttle around the turn. That was a mistake. People make mistakes on our streets every day and we should be putting in effort into making mistakes as low-cost as we can.
November 2024 Meetings
Monday Meeting Details
Monday, November 11th 6:30PM - 8:00PM
Juniper Kitchen in Dover
At this meeting we will be reviewing select projects from the Dover Capital Improvements Plan (CIP). Our goal is to familiarize ourselves with the CIP and find areas where we want to be actively involved in the conversation. We hope that reviewing this will help us align our advocacy with where the city’s attention is focused.
Saturday Meeting Details
Saturday, November 16th 10:30AM - 12:00PM
Dover Public Library Learning Center
After reviewing some of the options that we discussed in our last Saturday meeting, we think that addressing the graffiti is the most likely candidate for success. We will be meeting at the library and then walking around the downtown of Dover, identifying areas where there is graffiti and then bringing all of that evidence back to the library and submitting it to the city of Dover’s Committee for Graffiti Management to be removed.
Speed Increases the Risk and Cost of Mistakes
Along our transportation system there is one variable that can affect how costly a mistake is in a big way, and that is speed. Simply put, the faster a vehicle is traveling the more likely that a mistake will have severe consequences, especially on a street where you have mixed modes of travel. During a city meeting I attended, the following slide was presented in reference to roundabouts.
Two things are going on here, the first is that the amount of distance for a person in a vehicle to see and successfully respond to something in their path is significantly higher as speed increases. In fact, between 20MPH and 30MPH it nearly doubles. The second is that in the event of a vehicle collision with a person, the risk of a fatality jumps dramatically with higher speeds. There is an 8x difference between 20MPH and 30MPH.
With those numbers in mind, I want you to think about how many 30MPH speed limits we have on our residential streets around the seacoast (it is actually the default speed limit unless posted otherwise). How many of them have crosswalks as an invitation for people to walk into the street where a mistake puts them at a 40% chance of fatality? Finally, how many people are actually driving the speed limit or below in these areas? We can make our streets safer by acknowledging that lower speeds should be the goal in areas that have mixed modes of transportation. The design of our streets can help with that.
Forgiving Design
In the book Confessions of a Recovering Engineer Chuck Marohn, the founder of Strong Towns, talks about a concept called “forgiving design”. He attributes this concept to saving thousands of lives on our interstate highway system because it uses the design of the road to “forgive” the mistakes of drivers. On the interstate system you have 12’ wide lanes, large shoulders, trees and obstacles have been cleared away from the road, and many other design elements that make driving at high speeds with a bunch of other cars around you, safer.
We do that same very thing on our streets and we apply similar designs and thinking to make it safer to drive, the problem is that not everyone is driving a vehicle and streets are not as simple of an environment as a road. We are combining the design elements of a highway with the complex environments of our streets. I’ve written before on how street design affects travel speeds, so I’ll sum it up as: the context of the street is more important in determining how fast people drive than the speed limits we impose.
We can still use the concept of making a forgiving design, and focus that forgiveness on our most vulnerable users of the transportation network, walkers and bikers. These two groups are the most at risk in the event of a mistake and therefore benefit the most from having their mistakes forgiven. Let’s make crossing the street less dangerous and make riding a bike along with vehicles comfortable and safe. We can do that by simply reducing vehicle speeds.
Twenty is Plenty
There is a popular campaign slogan for this advocacy called, “20 is Plenty” referring to the graphic that I shared above that shows that the cost of a mistake rises dramatically when vehicles travel faster than 20 MPH. Driving at this slower speed might sound a bit inconvenient, but driving faster than that creates inconvenience and dangerous conditions for people riding a bike or walking. If we want to create areas of successful multi-modal transportation then we need to have compatible speeds and 20MPH is a great meeting point.
We don’t need to do this everywhere, but in neighborhoods and residential streets, this is totally appropriate. In our downtowns and along streets that have multiple crosswalks, this is called for. Those places in our cities are already oriented towards people and we should be comfortable trading vehicle speeds for human safety.
Slower vehicles doesn’t have to mean less throughput either, designs such as roundabouts can create continuous flow for vehicles and increases in both walking and biking would count as throughput as well. When everyone is traveling a compatible speed it can really change the efficiency at which we move, eliminating dead stops such as traffic lights as a necessity to traverse an intersection. You can see an example of this in places like Peyton in the UK.
Conclusion
The slide at the beginning of this article highlights the drastic safety benefits of getting vehicles to drive slower and in areas of mixed modes of travel it can be a life saver. We can leverage the design of our streets to minimize the cost of mistakes. I know that this point intersects with a lot of my other arguments such as streets being safe enough for kids, walking and biking being better forms of transportation investment, and narrowing lanes making safer streets. All of these are single areas of focus of a larger argument for valuing the movement of people over the movement of vehicles in our streets. One of the keys to creating successful places is to make a place somewhere where people feel comfortable being at. I want to see us embrace our streets as places to be. When we design our downtown streets to encourage low speeds we encourage people to explore them outside of a vehicle.