This is a community post, untouched by our editors.

This post may feel like an out-of-context jump into the middle of a conversation if you haven’t already read the setup. It is also worth taking a look at the NSPE code of ethics that is the standard guide for professional engineers in the United States.

Fundamental canon #1 (of 6): Engineers, in the fulfillment of their professional duties, shall hold paramount the safety, health, and welfare of the public. Canon #1 dwarfs the next 5, and in fact the remaining canons all relate directly back to the welfare or interests of the public (see also design for the masses).

Typical signalized intersection with multiple turn lanes // Source: Andy Boenau

Generally, about half of vehicle crashes occur at intersections – and the most dangerous type of crash is the t-bone (turning vehicle hit on the driver’s side). In the United States, engineers use stop lights (so named because there is so little ‘going’) as their default solution for controlling traffic at busy and/or dangerous intersections. This despite the fact that the federal government and many other agencies actively promote the use of roundabouts for 20 years to improve traveler safety. The Insurance Institute for Highway Safety has been researching the life-saving benefits of roundabouts for years. The most obvious benefit – the reason they typically reduce fatal crashes by 90% or more – is that they eliminate the t-bone crashes.

The local officials who own and operate the intersection in the photo above have repeatedly rejected proposed roundabouts over the years. The reason? I’ve heard two directly from the decision makers: (1) politicians and residents might not like them, and (2) the roundabouts might not work here like they do other places. Meanwhile, the jurisdictions across the country who convert stop lights to roundabouts continue heaping evidence onto the federal government’s already strong case that roundabouts are the safest form of at-grade intersection.

Seeing a stop light installed at an intersection does not automatically point to unethical behavior by transportation engineers. But in my opinion, forcing engineers to prove the need for a roundabout as opposed to proving the need of a stop light is completely wrong. Looking back at the first canon of ethics, how can one claim to “hold paramount” the safety of the public when stop lights are generally considered the appropriate default intersection control? Imagine the following situation:

A decision maker (e.g. public works director) is presented with two nameless design options – Option 1 and Option 2. He is told Option 1 might be unfamiliar with some people and it will slow down traffic at the intersection. Option 2 is very familiar to drivers, but will kill a lot more people, destroy a lot more property, require far more money for maintenance, require additional lanes to be built over time making it harder for pedestrians to cross the street, will generate more pollution from stop-and-go conditions, and will require significant right-of-way for equipment. It sounds outrageous but Option 2 is the default decision for most public agencies in the United States. Maybe we should shift the national discussion on traffic safety from driver behavior (the proximate causes) to street design (the ultimate cause).

As a special bonus, take a look at this link if you think roundabouts are more complicated for drivers than stop lights.

Example of safest form of at-grade intersection // Source: Andy Boenau