The Ranty Highwayman)
I don’t hear this every day, but “just rephase the lights” has become a shorthand for people who cannot see or refuse to see that they are part of the problem.
First, let’s get the terminology right and I have the irrepressible Brian Deegan to thank for this wonderful three word description of how traffic signals are arranged;
“Phases make stages”
Phases come from the electronic set up of the signal control computer, essentially they refer to where traffic (drivers or cyclists) or pedestrians are are controlled through a junction on a predictable path with the control being the signals themselves. With pedestrian crossings and situations where opposing traffic flows always run together, then they are taken as single phases.
A stage is where non-conflicting phases can move together and may or may not be used each time in the signal cycle; with the signal cycle itself being basically where every called stage has had a turn (in a preset order). For the very geeky, a more detailed (and slightly more correct) explanation is available on a Traffic Advisory Leaflet here.
So, when people say “just rephase the lights” they probably mean they want the set up changed to favour a particular stage they have an issue with (the one they feel held up on). Rephasing would essentially come from a physical change to the layout because we are dealing with fixed paths or movements. Perhaps they do know more and think that a dedicated phase should be created for them and that it should always be green!
I am not entirely sure how the phrase has come into common use, but at the root of it is a dissatisfaction with how signalised junctions operate (and I never hear the phrase used with standalone signalised crossings). As the running title of this occasional series of posts suggests, we are dealing with something finite and as with a pie, it has to be divided up somehow. My generalised complainant just wants a larger slice.
The size of the pie is governed lots of variables which go back to physical space, the number of traffic lanes, pedestrian demands, cyclists demands, flows changing throughout the day, type of vehicles passing through etc. In essence, for any given situation there will be an optimum pie size. If we are to efficiently consume the pie, we will be able to scoff 90% of it easily without any problems. The last 10% is where people start fighting over the crumbs and it’s not efficiently eaten.
Paradoxically, we can sometimes eat more than 100% of the pie (and to be honest it’s where my analogy turns a bit suspect), but its people licking the enamel off the plate. The amount which the capacity is utilised is known as the Degree of Saturation (DoS) and so 90% DoS is generally the most efficient situation and as we reach (or sometimes exceed) 100% DoS we are in the realms of people taking shorter gaps, tailgating, jumping amber or red signals etc.