Visual perception at different speeds.

Visual perception at different speeds.

Our urban streets will not be safe until we slow cars. We won't make a significant dent in slowing cars if our toolbox is a combination of signage, more enforcement and driver education. Those are all nice, but the primary hurdle we need to overcome is our propensity to over-engineer, to apply highway thinking to local streets.

One of my favorite writers at Streets.MN is Bill Lindeke. Last week had a fantastic article on the subtle, but critical, difference between a 30 mph speed and a 20 mph speed. He perfectly explains why stroads (the street/road combination) are not just a suburban phenomenon but are actually pervasive throughout urban neighborhoods:

The problem is that for a good urban street, this muddy “middle ground” between ‘walkable’ and ‘driver’s paradise’ can sometimes be the worst of both worlds. And as I’ve been traveling around Saint Paul lately, I’ve noticed one particular aspect of street design where the city is about 80% of the way to designing a successful street. But much of the time, it’s the last 20% of the design is absolutely crucial to the outcome. I think of it as “the critical ten.”

He even deals with the biggest red herring: fear of delays in travel time.

At the same time, the big concern for many engineers, drivers and civic leaders is how lower speeds will impact traffic flow. They amazing thing is that it doesn’t have to make a huge difference. When you’re talking about traffic flow on these urban commercial streets, speed is far less important than delay at intersections.

And as we pointed out here quite some time ago, traffic signals are the epitome of orderly but dumb thinking.

Forgiving design principles used by engineers today are designed to forgive the mistakes of drivers. In our urban neighborhoods, we need to prioritize forgiving the mistakes of those outside of a car.