[104] in 6.033 discussion
Traffic Lights
jered@ATHENA.MIT.EDU (jered@ATHENA.MIT.EDU)
Mon May 13 23:52:51 1996
This seems vaguely reminiscent of one of the examples in Saltzer's lecture
last week. From the latest RISKS digest.
--Jered
Date: Fri, 10 May 1996 09:19:35 -0500
From: JEREMY J EPSTEIN <JEPSTEIN@mail.cordant.com>
Subject: Massive failure of Washington DC traffic lights
According to the 9 May 1996 *Washington Post*, most traffic lights in
downtown Washington D.C. went onto their weekend pattern (typical: 15
seconds of green per light), rather than their rush hour pattern (typical:
50 seconds of green per light). This occurred during the Wednesday (8 May)
morning rush hour. The problem was reportedly caused by a new version of
software installed in the central system that controls all of the traffic
lights, providing timing (so lights turn green in sequence). The result was
mile-long traffic jams. One woman reported that her 35-minute commute
turned into 75 minutes, due to the overloaded streets.
By the afternoon rush hour, the software glitch had been "fixed". It wasn't
clear whether that meant they reloaded the old software or fixed the bug.
Some might consider this a risk of computer controlled systems, and others
might consider it a substantial increase in the nation's productivity: think
of all the lawyers and congresscritters who couldn't get to work!
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