Posts Tagged 'requirements'

Missed or Changed Requirements

Editor’s Note: Author resides in British Columbia, Canada.

A brand-new, Light Rail Transit (LRT) system sprouted where I live this past year. The fantastically efficient, 2-car train passes the main stations every
3 minutes. The stations are smaller here than other LRT/subways that I have had the pleasure of using in other regions, because these trains pass through the stations so often.


In some stations you can see the train coming at high speed over the raised rail system for quite a distance. It smoothly arcs back and forth as it follows the curves so nicely.

There is no driver; the train is automated, and although it accelerates a little faster than I would expect and brakes too hard sometimes, it is otherwise quite smooth…except for the stretch between the middle two stations. This is the longest stretch of track and has two doglegs. The first dogleg turns left as you are going north, that is followed by a short, straight stretch, followed by a dogleg to the right.

A “dogleg” is a paired set of turns–first one direction, then the other. Technically you could say a “dogleg left” in a road would refer to a left turn of up to 90 degrees soon followed by another turn that is roughly equivalent in degrees to the right side.

Our train’s set of doglegs is fine…except for the forced braking that occurs, followed by a prolonged, high-pitched squealing as the train screeches through the turn. Why would the engineers design a set of corners on which the train was unable to make a smooth turn? Why would they not have banked the train more, so it could remain at the same speed as all the other sections of the track that are not in stations? Why did they have to put in these doglegs to go around something that seems to be directly in the path?

Were these missed requirements by the designers? Were these last minute changes to get the project done on time? This 15-17 mile LRT line runs quietly for all but two, 30-second blasts of squealing around the doglegs.
There are lots of other curved sections of the LRT that are silent and smooth. Why this mid-point anomaly?

It was a major surprise to have to suddenly sit through this cacophony of noise in a brand new system. The noise reminded me of the old trains I rode in many a foreign country, but they are totally out of place for a system built in 2009. I wonder how they explained this oddity to whoever was in-charge of the project.

Have you ever had a situation where requirements were missed or omitted?

Image courtesy of Adrian van Leen; rgbstock.com


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