Further Reading: The Big Picture

 Volume, Capacity and Congestion

          Aspen does not have a significant problem with traffic volume – which is the actual count of the number of vehicle trips - at the entrance to town.  Most medium sized towns have at least one major thoroughfare with traffic volumes comparable to Aspen. Montrose, a town on the West Slope of Colorado with a population of about 15,000, and only a fraction of Aspen’s tourist trade, has exactly the same number of average daily vehicle trips on their main street as Aspen, but they don’t have to put up with a mile long traffic jam, and they don’t even have a bus system.
          It is the relationship between traffic volume and highway capacity that determines the level of congestion, and only matching these two, or providing more capacity than you need, can work as a means to eliminate congestion.
          Although there are many features of the Entrance to Aspen which contribute to the traffic jams during peak periods, there is only one feature which is necessary and sufficient to create this level of congestion.
          To understand the dynamics involved, it is helpful to think in terms of water.  They don’t call it traffic “flow” for nothin’.  Fill a tube with flowing water, and pinch the far end, and you stop the water all the way back to where the water enters the tube – instantly.
          The merging of two lanes into one, whether inbound or outbound, fills the tube.  After that, anything which closes or even pinches the tube – traffic lights, S-curves, roundabouts, human reaction time, stray dogs, a couple of snowflakes, anything – guarantees that the effect is felt all the way to the end of the line.
          If more water can’t flow into the tube, you begin to form a reservoir.  This reservoir can then only be drained if you have a full blown drought upstream.  Applied to the entrance to town, once the one lane is full, and the backup begins, vehicles feeding into the reservoir never allow it to empty out until the volume of that traffic drops well below the capacity of a one lane road.  Both the length of time people must wait in line, and perhaps more significantly, the number of hours in the day that the backup lasts, are a direct result of the reservoir effect.
          It’s entirely possible that no other place in the United States has managed so much traffic congestion, with so little traffic volume, as has been achieved at the Entrance to Aspen.
          Although many people automatically offer support for mass transit as a solution for congestion, it really is a completely separate subject.  There is nothing about providing sufficient highway capacity that contradicts or prevents support for mass transit.  There is nothing about supporting mass transit that responds to the capacity problem, because no amount of mass transit will get Aspen down into the range of traffic volume that can be handled by a slow moving one lane road.
          Here is a simple way to think of the equation.  If you take two lanes and add two more, you’ve increased capacity, and potential for reduction of congestion, by 100 percent.  To achieve the same proportion of impact with mass transit, 50 percent of all vehicle trips would need to be converted to mass transit.  To their credit, not even the most ardent mass transit advocate has ever suggested that half of all vehicle trips can be turned into mass transit trips.
          Another way to look at the potential for a transit solution to relieve traffic congestion is that it isn’t even intended to work.  The current plan for the Entrance to Aspen is to leave the capacity at two lanes, while maintaining current traffic volumes, with the expectation that the continuing congestion will increase transit ridership.  Even assuming that inconveniencing people leads to a change in travel mode, the purpose in doing so obviously isn’t to reduce congestion.
          The city’s bus lane project is the short term strategy to try and eventually clog up the entrance permanently.  It will do nothing for outbound traffic congestion on Main Street, and will make the inbound situation even worse.  Remember, bus lanes are reserved for buses-only, 24 hours a day.  So, vehicles will still be forced to merge at Buttermilk, and a second choke point will be created as buses merge into the one lane at the roundabout.
          The question regarding whether to expand the entrance to Aspen to four lanes (that everyone can use) isn’t about whether to have more mass transit or not – there is no limit to that except the amount the public is willing to fund.  The entrance question is solely and completely this one:

Do you always want there to be a traffic jam at the Entrance to Aspen?

          If your answer is yes, support the city’s preferred alternative.

          If your answer is no, help the Entrance Solution campaign for a four lane alternative.

     Back to Entrance to Aspen Home