Moving beyond auto-centric tools for multimodal planning

Nice to see this article on BikePortland about that city's efforts to change what planners correctly note are unfair auto-centric metrics. You can't build multimodal, sustainable cities if the system is still be biased toward cars. And have no doubt that the vast majority of transportation engineers adhere strictly to the old manuals that put traffic flow above all else. This also relates to the projections fallacy I mentioned on the podcast last week calling into question traffic projections and our obsession with them. I have run into this obstacle in almost every street design project I've been involved in. According to most planners and virtually all engineers, street space can only be reallocated to pedestrians, cyclists or transit vehicles if it doesn't negatively impact those driving cars. It is reasonable to estimate traffic volumes, just as transit planners must estimate transit passenger volumes. However, traffic projections are usually wildly overestimated and ignore some important and undeniable facts. The most obvious discrepancy is that Vehicle Miles Traveled has declined for almost a decade. This trend will continue as more people choose to live in cities where they can rely on public and non-motorized transportation and live car-free.

Projections tend to ignore driver behavior and decision making. The assumption is that all of the current traffic will remain and we must make sure it keeps moving. However, traffic is fluid and changes significantly after changes are made to the street and highway networks. Since nobody is attached to a particular route, you will simply choose the best mode and route to get between points A and B. So when you design a road today to have 30 percent greater capacity, it will fill up tomorrow as more people find it faster and more convenient, and you will be wondering how you failed to predict the growth. (You will also ignore the decline in traffic on other routes and probably pull the same tricks there in the future.).

Traffic volumes reach an equilibrium as each individual finds the best way to reach his/her destination. This is true regardless of mode, and people often switch modes if they find that the calculation of variables -- time, money, stress, comfort, parking availability, etc. -- changes. Traffic volumes usually decline during road construction projects as drivers use other routes (or modes). Then, by the time the new road opens, it's not really needed or even justified.

Given all this, we should ask ourselves why we even bother making localized traffic projections when we know it only serves to prevent progress. Some people say we should have a bicycle LOS metric, but that misses the point. We should instead design streets for safety and a basic level of mobility for all road users (except transit which should receive top priority along with walking). This means taking space away from cars and giving it back to others. If car lanes or parking spaces have to go, so be it.