I’ve been following the progress of erstwhile streets.mn commenter and cartographic wunderkind Al Davison via Twitter as he has been putting together a map project showing the road diet potential of Saint Paul’s 4-lane streets. This kind of map is a big deal given the increased conversation around pedestrian safety in Saint Paul. (See also today’s post on the recent Maryland Avenue County meeting.)

Davison put together a map mashup using County and City ADT information and the Federal Highway Administration (FHWA) guidelines for road diets. Davison uses a broad definition of “road diet” to include a variety of different traffic calming measures.

Here’s the result. The color of the street represents the road diet feasibility ranking according to the FHWA, while the color of the stripe on the side represents the number of currently existing lanes:

I found the map so intriguing that I interviewed Davison about how he put it together.

[Transcript follows]

Q: Tell me about this map. Why did you make it?

Al Davison (AD): I just kept seeing articles articles about pedestrian safety and past fatalities so I got curious. Since I work at MnDOT and deal with data on a daily basis, I was curious to see if I could use data, see the daily traffic volume, and compare them to what you see on the FHWA data on road diets.

The main question was how many roads the city would be a possible candidate for a road diet. Since we have the data, I ended up using it, and even tho our data for thru lanes is outdated, I just did it myself.

And its pretty easy. Google aerial had updated photos, as recent as March 16, and I was able to look at those and least get the roads updated to the best of my knowledge.

Q: What dies the map tell you? What patterns did you end up finding?

AD: I see that especially along Interstate 94, there are a lot of 4 lanes roads. That’s because… there’s a lot that I know from personal experience, since I work in Saint Paul. I know especially near the freeways, that’s where a lot of the traffic is. And that tends to be where there is the higher volumes. And typically the roads are much wider. But at the same time, a road like Lexington is 3 lanes near 94 at one point.

And the same is true with Rice Street. But at the same time it makes it dangerous. It might be way too wide, even if it would increase traffic, I mean. Since I went to the U, and they did the road diet with Riverside… and I’ve driven on Riverside during rush hour. It’s a pain, but overall it’s safer compared with what it used to be there.

Q: How did you put this together? What was the process?

AD: It’s kind of more just a natural curiosity for myself. I like these little personal projects, but I usually just leave them as half finished. But since I had enough data available, I kept following through with this, and ended up with at least a basic map on potential sites for possible road diet.

Because I know, looking at the volumes along Rice and Dale Streets, they’re really not that high to the point where they need 4 lanes. I drive on Rice all the time and its not even safe as a driver with 4 lanes. On Rice, I’d rather have it be like it is near my house, where it’s basically a 3-lane pattern. And it even has higher traffic volumes there. It’s really not that bad, and I like it better. I’d rather have turn lanes, rather than having 2 lanes.

Every time I try to stop for a pedestrian at an unmarked intersection, I get worried because I do see a lot of times where people coming from the other direction don’t stop. It’s very unsafe for everybody.

Q: Final question… what software did you use?

AD: It’s a mixture of of ArcGIS and QGIS. I try to rely more on open source software, even though at work I use ArcGIS, and I’m used to dealing with it. When i do personal projects, I try to do them on open source applications. It’s a learning experience. And also, I just like making maps in general. I’ve always been interested in maps.

[transcript ends]

Thanks so much to Al for putting this together! I think it can be a useful starting point for future conversations about traffic calming in Saint Paul.