We took the whole reinventing government movement to heart and as a result we have tried to adopt a more customer centered approach to running the business of City services. That means responding to concerns more quickly and professionally. It means really listening to people and anticipating their needs in our service delivery. When you pride yourself on being a City government that works hard to listen to its customers, receiving citizen requests to put in new traffic signals can be downright painful. The customer service side of me wants to say — one new traffic signal coming right up — but thanks to that modern marvel of traffic signals I’ve come to see that there’s a difference between being responsive and being responsible. And when it comes to public safety that distinction can save lives.
I completely appreciate our customers’ desire for new traffic signals — I’m a driver too and as I wait for a gap from a side street I find myself wishing I had a signal to take advantage of. It’s inconvenient to wait and it feels less safe to have to shoot the gaps in traffic. Most of us certainly look at traffic signals as something that will make things safer for drivers but at the risk of oversimplification let me try to offer a little more of the traffic engineering thought process when it comes to new signal installations.
I know this may seem counter-intuitive — but traffic safety research shows very clearly that traffic signals will cause accidents, particularly rear-end accidents, as well as put driver’s at risk for other dangerous accidents — like red light running. Unfortunately, despite our hopes and best intentions in putting in new signals, the new signals will bring more accidents whether we like it or not.
I’m sure you’ve found yourself getting ready to pull out because you have the green only to have a car come screaming through in the other direction. It shouldn’t happen but it does and it happens frequently enough that the traffic engineers can actually predict with remarkable accuracy how often it will happen based on traffic volumes. I know we all think we have a unique intersection but when you study traffic accident data, driver behavior is fairly predictable and it shows that drivers hit more drivers at signalized intersections than anywhere else.
So before putting in a new signal the engineers have to be sure that the increase in the new accidents will be offset by the decrease in frequency or severity of accidents that are already happening at the intersection without a signal in place. There’s a highly refined statistical process that they use and in the end they use that data to determine if a new signal will make things safer or worse.
You might be surprised to learn that we run those traffic analyses and no matter how many ways we look at the data, it often comes back saying that a signal will result in more accidents at an intersection than are occurring today which is why we will often have to say no to our customers.
Saying no is no way to treat your customer if you’re trying to delight them but if you’re trying to keep them alive it is exactly what we have to say sometimes. That doesn’t necessarily make it any easier to say but with the stakes so high we definitely don’t want to put them in greater harm. Honestly, if we didn’t care about the safety of our customers it would be easier on all of us to not take the unpopular position of saying no to a new signal but we just can not sacrifice safety in the interest of expediency or convenience.
With the invention of traffic signals some 90 years ago in our own backyard in Cleveland, I guess we’ve got no one to blame but ourselves. There are days when I wish Mr. William Phelps Eno had been right in 1928 when he observed that “…students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail.”
From the City of Scottsdale Arizona Transportation Department
Traffic signals always decrease congestion and delay for some vehicles, and always increase delay and congestion for other vehicles. By definition, a green light for some traffic is a red light for other traffic. Signals typically reduce certain types of accidents and increase other types of accidents. Prior to the installation of a traffic signal in Scottsdale, a thorough study is completed that analyzes the anticipated advantages and disadvantages of the proposed signal.
The procedure utilized was developed by the Federal Highway Administration. It consists of eight separate, but related warrants (sets of criteria). The primary consideration is the traffic volumes on each of the approaches to the intersection. An equally important factor is the accident history at the intersection. The proximity of other traffic signals is also considered. The presence of pedestrians, schools, hospitals, and other similar considerations are also analyzed.
From Indiana DOT
One should do what one reasonably can, but refrain from making conditions worse by doing something for the sake of appearing to “do something” (physician’s “primum non nocere” principle), and one should consider all practical solutions at one’s disposal.
Unfortunately, heavy reliance on single-access design for suburban residential subdivisions has limited residents’ escape options and reinforced the misconception that the only proper way to access destinations to a driver’s left at an unsignalized intersection is just to suck it up and execute a left turn onto the arterial roadway, at whatever risk to life, limb, and carriage.
Making a series of right turns is apt to be less conflict-prone than executing
a left turn at an unsignalized intersection, but on a one-mile superblock could
require three miles of additional travel (one way). Simply providing access
connections out the back and sides of a subdivision may greatly reduce the
inconvenience of alternative routes.
For costs less than or comparable to those of installing a signal, it may also
be feasible to make geometric adjustments at the intersection of concern so
that left turns can be made with less anxiety.
What “feels good” or “feels like” is not a reliable indicator of safety
performance of a proposed traffic signal, and making an exception to warrants (if no warrant is satisfied) is to embark on a slippery slope.
A signal works primarily by stopping traffic. Anytime a car stops on a highway, the possibility exists that a following motorist will not notice the stopped vehicle until it is too late to avoid a crash.
We have seen that a traffic signal is not a cure-all. It may solve some problems at an intersection, but it may contribute to others. A signal at the wrong location can cause crashes or congestion, or both. For this reason, your safety requires that INDOT investigate each signal request carefully.
From Utah DOT
Traffic signals are often perceived to be a “cure-all” for all traffic related problems at intersections. Unfortunately this is not the case as unjustified traffic signals can adversely affect the safety and efficiency of vehicular, bicycle, and pedestrian traffic.
It turns out that Mr. Eno was wrong and everywhere I’ve worked new signal installation requests have been full of stress for everyone involved so I have to admit that they are one of the least favorite aspects of my job. But it’s not just a Kent-thing, here’s a sampling of signal stuff from other cities: