They didn't over-engineer those roads

Infrastructure jargon is full of subtle manipulations.

Civil engineers often describe their finished projects as "over-engineered," implying they are overly safe and robust. They’ve gone the extra mile. The calculations said one steel beam was enough, but they used two. 

When it comes to surface streets meant for public access, can a street ever be too safe? And considering traffic casualties are an equivalent of a 9/11 every month, year after year, who would even try claiming streets are overly safe?

The standard multi-lane arterial is designed for high-speed driving, but also expected to accommodate bicyclists and pedestrians from surrounding areas. Decades of research shows this type of design leads to more and deadlier crashes, especially for vulnerable road users.

Source: National Highway Traffic Safety Administration

A pedestrian hit by a 40 mph car is almost guaranteed to die. A pedestrian hit at 20 mph is almost guaranteed to survive. Curious then, that the standard American arterial is posted at 45 mph. So for drivers who follow the rules, a crash with someone walking will almost always be deadly. 

The 40-20 Rule of traffic safety

But take traffic law obedience out of the mix. The road itself is typically designed for much higher speeds than the posted signs. Engineers are trained to design width, curves, and sightlines for motorists to feel comfortable going much faster than a law might allow. Even the style, fonts, and placement of signs and lights are intended for high speed driving. 

A road is under-engineered when it doesn't account for the threat to people walking and bicycling. It's under-engineered when it ignores neighborhood context. 

Sacrificing safety for speed is under-engineering. Over-engineering would be in the direction of protected bike lanes, placemaking, and traffic calming.

Not all arterials are the same, regardless of what a DOT design manual claims. Some make sense for long-distance trips and higher speeds, but not when they’re used for local trips in population clusters.

Language matters. Listen for the subtle manipulation of terms like over-engineered.