Quotables 3: Speed tables and crosswalks
Drivers need more than just paint to see what's going on.
If you think it needs a high visibility crosswalk, it probably needs a speed table under it.
This one came from my friend, Veronica Davis last year at TRB. She may be famous for being an equity expert, but you won’t find a better engineer. We were talking about slowing drivers down and she quipped, “The only thing that slows my drivers down is a speed table!” Working in Houston, that wasn’t a surprise, but it was an epiphany.
The best thing about a speed table is that it focuses your attention right there. You have to moderate your speed getting to it. You have to watch it until you get over it. If you’ve got your driver’s attention, use it! They’re already staring at it. Give them something worth looking at.
If people are going to cross in a place you don’t want them to cross, this is “need to know” information for the driver, so make sure they can’t miss it. Hitting someone could kill them, but it will also leave the driver with nightmares for weeks.
Don’t get me wrong. I hate speed tables.
I have avoided recommending speed tables for years. Most of the time they’re a band-aid on a gaping chest wound. We use them when drivers are annoying the people around them and we run out of ideas to “fix” it. The reason they work is because you can’t break the natural laws of physics—you will only break yourself against them. It’s the classic case of pain management instead of the cancer treatment you really need.
Here’s the reality: drivers will use the speed they think is safe for themselves and others. If they can’t see anyone else they would hurt, they won’t drive like they could. If they’re going over 20 mph, they’re only going to see about half of the people that are walking around. If the driver can’t see them, it’s as if they don’t exist.
If there’s no one on the street that they can see, drivers will not slow down. If the buildings are set way back or behind a parking lot, who is at risk? No one they can see. If they’re speeding through a neighborhood, it’s because they don’t see anyone there to care about and the road is plenty wide enough to keep from hitting anyone on the sidewalk.
There are two solutions:
Throw up speed tables
Reclaim the road.
The speed table sledgehammer.
A speed table is a sledgehammer approach to the problem. It will work, but it’s a brute force approach that leaves everyone miserable. It ruins your emergency response time. It annoys the drivers. It messes up your drainage. They’re ugly and they only work right where you put them.
When you just throw up a speed table, drivers will slow down at the speed table and then try to make up time between them. This is what it looks like:
They graphed how fast people went in the mid-blocks with different spacing and created formulas for how far to space speed tables to get the speed you want. I’ve converted the equations to US measurements. (You’re welcome—it’s been 30 years since I’ve had to do that kind of algebra and I didn’t get it right the first time).
The problem is that your drivers will be staring at your speed table, not the people on the side of the street—and fuming as they do it. Grumpy drivers make mistakes. Put the speed table under a crosswalk and it makes sense. No one begrudges them if they can see the reason you need them.
Show don’t tell.
Designing a road is like writing a novel. Don’t tell the reader what’s going on—show them. Bad writers will pen, “Carrie was sad and lonely.” Good writers will give you: “A single tear escaped from Carrie’s eyes, disappearing into the suds covering the lone dish in the sink.” They create an image that conveys more than just the facts.
For a roadway design, you have to make the context obvious so drivers know what you want them to do. New quotable:
A picture is worth a thousand words—and a vibrant context will work better than a thousand warning signs.
If you want them to slow down, you can start by making it look narrow. Tunnel things down so that drivers know they’re not in charge there.
Turn the road slightly so they can see a house in front of them instead of an open road. Keep the street narrow and pull the sidewalk out into it at the corners to reinforce the point. Keep the blocks short. Paint the intersection with a local icon worth looking at. Make sure the doorways are obvious and there are a lot of them. Throw a block party every 6 months and close the street down to one lane or less. Put up a basketball hoop and let kids play in the street again—beats PlayStation any day.
If you have something you need to draw attention to, flank it with speed tables and put a crosswalk on top of them. Here’s a great example near my best friend’s house:
They used the speed hump to highlight the fact that there’s a park there. The road is too wide and a little too open. The on-street parking makes it look wider. The colored speed hump points out the different context. There’s another one not too far down the road on the other edge of the park. This is a common cut-through route that would make the park unusable for the locals if they didn’t have the extra friction. the kids use it to cross. It’s not ideal for a stroller, but they just haven’t thought that far ahead—this was a band-aid that probably could have used stitches. It will leave a slightly larger scar, but it stopped the bleeding. I’d give it a B+.
Up Next:
We’re going to see snow in the mountains next week, so it’s 50/50 whether I’ll get a post out. We’ll see. I have a list of about 20 quotables I could pull, so it’s not like there isn’t more to write on. Feel free to leave any requests in the chat.