Sunday, November 27, 2011

Bottlenecks: Never assume the experts know better

As the saying goes: "Experts built the TitanicAmateurs built the Ark."


It seems to be human nature to rely on experts and not question their decisions. After all, if they are so clever, who are we to question them?


But sometimes it seems that they are self declared experts and/or it is us who declare them as experts and then believe our own prophecies.


Jerusalem has 2 new fast transport systems: A light rail and express buses. The aim is to eventually replace the latter with another line or 2 of trams.


I always wondered what was the advantage of transport-by-rail - especially intra-city where speed is not an issue.


Light rails are great when they work; the idea is that cars and pedestrians have to keep out of their way, as the trams are inflexible. They are quiet and don't need to tank up as they are electric.


Two weeks ago I saw that anything travelling on rails suffers from the typical bottleneck problem, as to be expected.


First I saw a train that had started pulling out the station and got stuck; I have no idea what precisely happened. For about 20 minutes it simply stood there. It was jam-packed and nobody was allowed off. Eventually the driver came around to the cabin at the back of the rain and drove it back to the station and let everybody off.


So what happens to the other trains? They have no way around the stuck train, so essentially all transport  heading North was stopped. It was a matter of time until all South bound traffic followed, obviously. (There are a few places where the North and South bound rails have an option to cross over; but running the trains in both directions on the same rail doesn't sound like a great idea.)


Later that day was one of the biggest funerals that Jerusalem has seen. It was close to the rail line. It brought the train system to its knees - for the second time in the same day. Since everybody wanted to get on the train, the train got stuck at every station, as the doors don't close if people are in the way. I sat watching the electronic devices inform us the the next train was in 10 minutes, then 15 minutes and then.... it announced "train stopped". It took 45 minutes for the train to arrive.


Despite them announcing that the next train was right behind (and probably 3 more behind that one) everybody tried to get on this one!


Buses are way more efficient! I often seen 3 buses play leap frog; one fills up at a bus stop while its twins head for the next stops.


Even in the express bus lanes, a bus will overtake another, if the first bus is stuck or taking too long to move.


There is a way to get both the advantages of quiet electric transport and not have to deal with rails.


In Johannesburg they used to have (and probably still do, but I have not been there in over 20 years) double decker electric buses with 2 antennas connected to the overhead electric lines. If a bus got stuck it could be unhitched from the wires and other buses could get by. 


They also had to do load balancing; if too many buses were behind each other trying to get up some of the steeper hills, then they all would get stuck unless some of them stopped, giving the power back to the ones in front.


Maybe the light rail was not such a brilliant idea after all...



1 comment:

  1. Hear, hear.

    I also never understood why inflexible, expensive infrastructure, like the rail is considered better than buses. Even the advantage of it being quiet is somewhat dubious, since it means there is an added danger element of people not hearing them coming...

    ReplyDelete