Timers or Sensors? The Traffic Light Dilemma
The one thing a motorist fears above all else, is being late to get nowhere. Doesn't it always seem when you're in a rush to get somewhere, you just seem to catch every single red-light on your way? You always sit at them for what seems the longest time, and you quick glance at the clock on dashboard and back at the light...it's still red. Finally the intersecting light turns yellow and you begin to ease of the brake, ready to take off. Sensors for traffic lights seem to be the wave of the future, while some areas still cling to timed lights, believing them to be most efficient. But probably worse are the areas that utilize both sensors and timers, where nothing ever seems to work out.
Let's start off with the sensored lights (ha..censored...anyway) - the lights are based on detecting the presence of a vehicle waiting over the grid (usually visible from the pavement) and signals to the light that traffic is waiting. Depending on traffic on the intersecting street, the light may change immediately to green to prevent an unnecessary halt in moving traffic. These generally provide excellent traffic flow for most streets that go distances between lights. In areas with more lights per/mile ratio, they can sometimes hinder flow by changing at improper times for intersecting streets. Sensors can also hinder traffic by not really being very sensor oriented at all. Many sensor lights still function on a timer of sorts, and even with sensors, people can be left waiting at lights for a long time, despite there not being any intersecting traffic.
Then there are timed lights. They can be as simple as being on a fixed time, being synchronized to all change at the same time or coordinated where they turn green in waves, so as to allow a driver to catch long strings of green.
Timed lights can be great (in terms of those coordinated) but can be a major pain in the ass when they're either of the other two. In high congestion all forms of timed can be both a blessing and a curse. Once again there's the advantages and the disadvantages. Generally they're all based on the posted speed limit, so if you're in a rush, you'll miss the advantages of coordinated/synchronized and end up sitting at all the reds anyway. However, with emergency vehicles being given the ability to change a light to green for obvious safety concerns, it can defeat the purposes of the lights being sync'd up, and cause unnecessary traffic.
But what takes the cake on a failed idea, is the marriage of these two ideas. Implementing an attempt at sync'ing lights. In my area, they've done just this, only a bypass where the speed is 55 mph. The lights are designed to be coordinated, but since some of the intersecting streets along the way have sensors, the coordination fails to work, and some instances even the sensors fail to work. I guess that's where this rambling has gotten me to...
I'm upset that more attention is paid to traffic signals by the DoT. Lights designed to be co-ordinated should be re-sync'd every night at midnight or something similar in order to re-establish co-ordination should it be altered by an emergency vehicle. Sensored lights should be periodically checked from time to time to ensure their effectiveness. Intersections should also be more frequently assessed for changes in traffic patterns, to ensure that sensors and timers are more effective at intersections.
Of course, all this is unrealistic as the cost to do something so large scale, across the entire country would be vastly expensive...perhaps they should just do it in my neighborhood ;-)
End Rant!
Slimee, signing out.
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