Calm down those dangerous arterials

In spite of what many engineers will tell you, those awful 45 mph, 4/6/8-lane speedways can be calmed down.

If someone tells you that traffic on busy roads can't or shouldn't be calmed, they're either lying or ignorant. 

Not only is it permissible for state and local agencies to calm their arterials, the US Department of Transportation has been offering technical support and funding for years. I expect social media randos to be uninformed about technical stuff like this, but so many professionals who work for state DOTs either don’t know about calming arterials or dismiss it as something they aren’t interested in. 

It doesn’t take much for distorted or outright false information to spread. One mentor tells two young professionals that arterials are to remain high speed. Those young professionals pass that along to colleagues and clients. Over the years, those two professionals become mentors and the cycle continues. It’s a large-scale variation on the phone game we played as kids (or at awkward corporate teambuilding events). 

Dangerous arterial in Florida (source: Google Street View)

The classic American arterial, notorious for its free-wheeling commuter traffic, intersections the size of city blocks, and backups caused by crashes, can absolutely be calmed. But don’t take my word for it like I’m some kind of omniscient mentor. Be skeptical, trust but verify, assume little and confirm much. 

The Federal government gives more than lip service about traffic calming. They offer free educational material and case studies for normies, free technical resources for engineers, and piles of cash in grants every year.

I have plenty of grievances with the Feds. After all, they still give hundreds of millions of dollars to state and local agencies that will be used to make arterials more dangerous. Imagine if I gave you $100 for groceries, but made you spend $80 or $90 on junk food. If it was your only way to get food, you’d keep taking the money but you’d also be growing unhealthy with time. But hey, let’s make the most of the good stuff.

When I bring up engineering ways of saving precious lives and valuable property, the most common pushback I get is something like “but that technique is just for neighborhood streets, not important arterials.” First of all, it’s funny to me that safety improvements are only needed on already safe streets. Second, the claim is wrong. 

“There is no prohibition on traffic calming on major arterials.”

—U.S. Department of Transportation

USDOT maintains a humongous online library with details on 28 proven safety strategies.

The entire list might not be relevant for you, but I summarized six that are probably vital for all of us.

1. Road safety audits. The best place to start. RSAs are performed by a multidisciplinary team evaluating all aspects of road user safety, including human factors and the capabilities of different road users. An RSA will always have transportation engineers on hand, but it’s also normal to invite the fire department, health department, transit agency, and a safe routes to school coordinator.

2. Speed management. Managing speed is crucial for reducing fatalities and serious injuries. People often drive fast even in densely populated areas, because they think they’re in full control of their car. They don’t, and they keep slamming into other people at lethal speeds. A person in the crosswalk hit by a driver going 30 mph has a 45% chance of serious injury or death. That risk drops to 5% at 20 mph. (Fun fact: along with engineering changes, the City of Seattle put a 25 mph speed limit on 200 miles of arterials.)

3. Road diets. Reconfiguring a street can be one of the most affordable safety transformations at your disposal. Sometimes it involves shrinking the curb-to-curb distance, but sometimes it’s just reorganizing who gets to travel in which space. Instead of two general purpose lanes in each direction, you might restripe to one general purpose lane in each direction with physically separated bike lanes on either side. Or you keep one general purpose lane in each direction and convert the outside lanes to transit-only lanes (where bikes are also allowed). 

4. Roundabouts. Converting stop-controlled and signalized intersections to roundabouts can reduce life-altering crashes by close to 80%. (Some report crash reduction percentages in the 90s!) Roundabouts work well in urban, suburban, and rural areas. Design details are important, but they lower vehicle speeds and the number of conflict points. It can be safer for everyone—walking, rolling, cycling, and driving.

5. Pedestrian refuges. Medians and refuge islands are particularly important for vulnerable road users. Every year, almost one in five crashes involves a pedestrian, and most happen away from intersections. People are trying to judge the speed of motor vehicles, predict what drivers will do, find gaps in traffic, and pray the drivers aren’t distracted. Designing a safe spot in the middle of the street can drop pedestrian crashes about 50%.

6. Bike lanes. That’s right, bike lanes are a way to calm vehicular traffic. On arterials, separating bikes and cars can be an important part of a network that’s comfortable for all ages and abilities. USDOT found that even just using paint and flexible posts as separation can cut car-vs-bike crashes in half.

Basic paint & post bike lanes are a low-cost, high-value treatment (source: FHWA)

Now that you’ve gone through all these engineering resources, I’ll remind you that local planning rules like zoning are the ultimate reason that we have to deal with car-oriented arterials. If you were writing a dramatic screenplay about dangerous infrastructure, traffic engineers and road designers would be some of the henchmen, and a planner would be the main bad guy. But that’s an article for another day.