engineering and ethics

Case 34: Roundabouts

Roadway intersections present several engineering challenges. Consider, for instance, that in 2009,20.8 percent of roadway fatalities in the United States occurred at intersections, or were in some way intersection related.116Signaled intersections are problematic for drivers, since a good deal of attention and thought may be required to traverse busy intersection. Drivers must decide quickly when and how to proceed, especially when facing a changing light, or when navigating multiple traffic lanes. Consider as well that stop-and-go traffic, such as traffic at a busy intersection, increases auto-mobile emissions significantly and results in traffic congestion. Both of these issues raise significant problems for engineers, since safety and efficiency are primary engineering concerns. Roundabouts provide an elegant solution to many of these problems. Roundabouts are circular intersections designed to allow vehicles to traverse in any direction, often without ever coming to a complete halt. The process of traversing a roundabout is very straightforward, with drivers simply following the one-way circular roadway to their chosen exit without having to worry about changing lights or multiple turn-Ing lanes. In addition, because cars must travel in a fairly tight circle, drivers are forced to reduce their speed. These two factors together make accidents, both vehicular and pedestrian, less likely. The design of the roundabout also helps to prevent some of the most dangerous kinds of accidents, such as T-bone collisions, in which a vehicle passing through a standard intersection is struck by another vehicle moving perpendicular to it. It is therefore unsurprising that a study by the Insurance Institute for Highway Safety found that replacing standard intersections mediated by stop signs or signals with roundabout intersections resulted in a 37 percent overall reduction in intersection collisions, and a full 90 percent reduction in fatalcollisions.117In addition to safety improvements, roundabout intersections are also more efficient. Unlike at standard intersections, vehicles are not required to decelerate and accelerate repeatedly, but can usually proceed without stopping. This enhances fuel economy and also reduces traffic delays associated with standard intersection designs. Roundabouts can also typically handle traffic using fewer lanes than signaled intersections, typically making them smaller. Finally, round-abouts are financially efficient. Because no signals are employed, maintenance and electrical costs are significantly reduced. Given these benefits, the roundabout looks like an engineers dream a simple, low-cost design that provides holistic improvements in safety and efficiency. The story is complicated, however, by the needs of visually impaired pedestrians. Navigating intersections is already a challenge for blind and visually impaired pedestrians, for obvious reasons. However, it is fairly easy to provide accessible crossing for them at signaled intersections. Many sig-nailed intersections are equipped with crossing assistance systems that provide audible cues to help visually impaired individuals know when to cross. Even intersections mediated by stop signs can be effectively navigated by careful attention to the sounds of oncoming vehicles. Roundabouts, however, are much more challenging for the visually impaired. Audible crossing assistance is untenable at roundabouts, since there is typically no traffic signal with which to intel-grate such a system. Even worse, the fact that traffic in a roundabout is constant means that auditory cues of oncoming traffic are very easily lost in the din of vehicles moving around the circular roadway. These fac-tors, in combination with the orientation challenges posed by the unusual geometry of roundabout cross-Ings, make navigating a roundabout on foot much more dangerous for the visually impaired.118However, someone might ask, Why should the concerns of the visually impaired be of any great sig-nuisance here? After all, visually impaired individuals represent a small minority of the overall population. Surely, the inconvenience of finding an alternative route for the disabled is a small price to pay for all the benefits roundabouts provide in terms of general safety and efficiency. One answer is the Americans with Disabilities Act (ADA). The ADA mandates that all transportation facilities be equally accessible to both able-bodied and disabled citizens. Failure to comply with the ADA can be quite costly, with legal damages between $55,000 and $110,000 beingstandard.119But, even without considering the ADA, concerns of professional ethics exist that are relevant to these issues. Commitment to safety is a ubiquitous feature of professional engineering codes of conduct. While the visually impaired are, indeed, a minority in the United States, their safety is, nevertheless, threatened by standard roundabout design. Equality and accessibility are also strongly valued by American culture at large. Insofar as engineers are required to consider the values of the public who utilize what they design, such strong values should be respected. These conflicting interests of safety, efficiency, financial risk, and equal access make roundabouts a difficult issue for engineers. Should we therefore a ban-don the idea, and rely only on standard sign and signal mediated intersections? Perhaps. However, one might also look at the issues surrounding access for the visually impaired as an opportunity for further innovation. And, indeed, much work has been done in developing roundabouts that retain the benefits described above while also providing easier access for the disabled. Many ideas have been explored, but two in particular serve to draw attention to the interplay of conflicting interests in this case.