Why Hierarchical Road Systems Are Good

A topic that has arisen a few times is the New Urbanism concept of a using a grid street system to disperse traffic rather than concentrate most traffic on a few major arterials with a hierarchical road system. This is one element of New Urbanism that I disagree with.

I’m not at all opposed to street grids, I am opposed to using them to disperse traffic since I believe that this promotes driving and will keep bicycling from being a viable option for the vast majority of our population.

Safety and comfort are requirements

Most average people feel unsafe and uncomfortable riding a bicycle in close and unprotected proximity to a lot of fast cars. Trucks add an even greater level of discomfort. The faster cars are going (and the more cars there are) the more we desire and need protection from them.

The Dutch have determined, after decades of pushing the limits, that people’s comfort level sharing a road with cars quickly decreases when cars are traveling faster than about 18 mph. So, above 18 mph their code now requires a minimum of a painted bike lane (though a segregated path or cycletrack is recommended). Above 30 mph requires a physically segregated path or cycletrack and the distance of separation increases with increases in speed. Note that these are actual speeds not just posted.

While most people are likely comfortable sharing the road with cars traveling 16 mph and nearly as many at 18 mph, very few, perhaps only a quarter, are likely comfortable doing so with 30 mph traffic and many fewer at 35 mph. Keep in mind that this does not mean that this many people will ride, only that this many people would be comfortable doing so.

So, if you are planning a street with 30 mph traffic and install no bicycle facilities you’ve likely eliminated about half to three-quarters of the population from riding a bicycle right from the start. Even a painted bike lane will only provide a feeling of safety and comfort to a very few more. A cycletrack however might be comfortable for nearly all.

New Urban-ing Summit Hill

Consider east-west traffic in Summit Hill that we previously discussed in St Paul Bicycle Plan: Completing The Local Mile, everything from St Clair north to 94. Assuming that traffic on each residential street is about 800 cars per day then we have 57,000 vehicles per day wanting to travel east or west in this area[1].

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If we take 1/3 of the traffic on the six arterials and disperse it among the residential streets they’ll now average about 2,000 cars per day on each. At the same time we’ve reduced the traffic on the arterials so Selby is now about 4,000 instead of 6,000. Good for Selby, not so good for Goodrich and other residential streets.

If we achieve New Urbanist Utopia then traffic will be evenly dispersed and we’ll no longer have arterials. Each of these streets will now have 3,000 vehicles rolling along them each day. To be fair, New Urbanists would like to see a lot more people walking so let’s assume that a third of all of these folks stop driving so now we’re at about 2,000 cars per day on each street.

Problem for bicyclists

The simple increase in traffic volume on these residential streets is a bit of a problem though likely not huge. It makes them a bit less comfortable to ride a bicycle and increases noise and air pollution. The biggest concern for most bicycle riders with increased volume will likely be at intersections. Even so, many Dutch engineers will still put a cycletrack on a street with 18 mph speeds but higher volumes.

Dutch cities want most of their streets to be pleasant and safe for bicycling without the need of special facilities.

Dutch cities want most of their streets to be pleasant and safe for bicycling without the need of special facilities.

The type of traffic, the type of people driving the extra 1200 cars, is a much bigger concern. How fast are they driving and how well are they paying attention?

Someone just leaving or arriving at their destination, especially if on a street they live on, is likely to drive a bit slower, pay better attention, and be more considerate of others.

Someone using a street as a thoroughfare has a very different mindset. This especially if they’ve already been delayed a bit and are using this residential street as a rat-run to bypass the arterial traffic.

How comfortable are you riding your bicycle on a street with only local drivers vs about three times as many drivers and with two-thirds of them people from elsewhere in a hurry to get somewhere else? How comfortable sending your 8-year-old out on this street?

Problem for drivers

If we want to be able to ride bicycles more and have others do so then we need to make it feel safe and comfortable on every street. We can either reduce traffic volume and speed enough that most people are comfortable sharing the road with cars and having their children do so (alone), or we can install facilities like cycletracks.

Now, what to do with the 40,000 people who don’t live in this area and aren’t driving to someplace in this area? The 40,000 people who are in a hurry to get from somewhere else to somewhere else? These people need a place where they can safely drive 30 or 35 mph and where people walking and riding bicycles are safe from them. If it’s not provided they’ll simply turn our residential streets in to arterials.

Do we slow all streets to 18 mph? Do we put a cycletrack on every street so that people can use them all as a through-way?

But, but, we’re creating car sewers!

Yes. Instead of the sewage being scattered all over doing all kinds of random harm we’re keeping it in one place where we can deal with it appropriately[2].

Good safe segregated bicycle, disabled and pedestrian facilities and other measures to mitigate the impact of a lot of fast motor traffic aren’t inexpensive and the cost doesn’t really change based on the volume of traffic.

A residential street with a few hundred local cars per day can be made quite safe and comfortable fairly inexpensively with 15-20 mph speed limits, shortening of the distances that can be travelled by car, maybe some no-passing rules, some chicanes and other elements.

A street carrying more and faster through traffic is a different animal. Here we need to segregate bicycle riders, pedestrians, and disabled from cars for them to feel and be safe and comfortable so we’ll need cycletracks and good sidewalks. Buildings along here might want some additional sound proofing. It makes little difference if there are 4,000 cars per day (Selby reduced by one third) or 14,300 (Grand currently). The impact of motor traffic is about the same and the needs and costs for mitigation will be about the same.

As much as we might want it, there really is no good in-between that I’m aware of.


I think we’re much better off in our example with 13 residential streets that are comfortable for all and only need cycletracks on six stroads rather than have 19 streets/stroads that are all uncomfortable and all in need of cycletracks.

Some might consider this all very unfair. We’ve chosen some streets to be quite pleasant and others to be car sewers. I don’t know that we have much choice. More, I don’t know that our car sewers can’t be made fairly pleasant as well with cycletracks, trees, and other elements that soften the impact of the cars and make them feel instead rather vibrant. Best of all, if we make bicycling comfortable then we may well succeed in significantly reducing the number of cars going down our sewers.


[1] I was not able to obtain accurate counts for these streets. Best guess is probably about 800 on average.

[2] This is kind of like building a big window well. The builder will often run drain tile (perf pipe) through the window well and then run the drain tile in to a sump pump inside the basement. Seems illogical because the goal is to keep water OUT of the basement. By doing this though the builder gains control of the water and can now safely direct it to where it should go.


Thanks to David, David, Reuben, Bill, and Marven for your valuable input.

Walker Angell

About Walker Angell

Walker Angell is a writer who focuses mostly on social and cultural comparisons of the U.S. and Europe. He occasionally blogs at localmile.org, a blog focused on everyday bicycling and local infrastructure for people who don’t have a chamois in their shorts. And on twitter @LocalMileMN