tag:blogger.com,1999:blog-5377014210518433927.post301238465525529960..comments2008-10-01T14:59:47.566-04:00Comments on Infosnack Headquarters: Metrorail Breaks Down Twice as Often as NYC's Wors... Michaelhttp://www.blogger.com/profile/15057113283154126104michael@infosnack.orgBlogger5125tag:blogger.com,1999:blog-5377014210518433927.post-4766388561821812842008-10-01T14:59:00.000-04:002008-10-01T14:59:00.000-04:00The average age of NYC's subway car fleet may now ... The average age of NYC's subway car fleet may now be significantly younger than WMATA's car fleet. NYC Transit's new cars are required to meet a MDBF performance figure of over 100,000 miles for a few years after purchase. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-5377014210518433927.post-80609989776143460892008-09-29T20:55:00.000-04:002008-09-29T20:55:00.000-04:00WMATA's asking for $11B in new funding over the ne... WMATA's asking for $11B in new funding over the next 10 years. People are going to want to know how reliable or unreliable the service is for determining how to react. <BR/><BR/>I think it's interesting that WMATA reports much better numbers in the annual report (on par with NYC Transit)<BR/><BR/>Can you think of a better way to estimate the reliability based on the data I have? Number of miles total compared to failures = MDBF? Michaelhttp://www.blogger.com/profile/15057113283154126104noreply@blogger.comtag:blogger.com,1999:blog-5377014210518433927.post-67934461376659001112008-09-29T20:18:00.000-04:002008-09-29T20:18:00.000-04:00Sometimes(!) mean + x stdevs is what matters.I sti... Sometimes(!) mean + x stdevs is what matters.<BR/>I still think that the standard deviation, or at least the frequency, is reasonable, given that you could be late home once, late to work once, and late on the weekend once, in a year, and I suspect that would be fine.<BR/><BR/>Perhaps other mass transit systems have better reliability, but many do not, and many non-mass transit systems (such as driving 20 miles to work, like lots of people do) have vastly higher variances.<BR/><BR/>Just playing Devil's Advocate here. Marknoreply@blogger.comtag:blogger.com,1999:blog-5377014210518433927.post-36664542529154565192008-09-29T13:56:00.000-04:002008-09-29T13:56:00.000-04:00Except that other transit systems have much better... Except that other transit systems have much better performance, that's true. And the affect on ridership is related to the deviation from the mean, rather than the mean trip length. Michaelhttp://www.blogger.com/profile/15057113283154126104noreply@blogger.comtag:blogger.com,1999:blog-5377014210518433927.post-4525342510670330932008-09-29T11:07:00.000-04:002008-09-29T11:07:00.000-04:00"an average WMATA rider could expect to be on a tr... "an average WMATA rider could expect to be on a train that is delayed 10 minutes or more three times per year."<BR/><BR/>Honestly, this doesn't seem too terrible to me. Out of 500 (?) trips, only 3 are delayed? Considering the value of ubiquitous, frequent trains, this seems reasonable. <BR/><BR/>If we assume an average 20 minute trip, plus a five minute wait, then people are spending 12,500 minutes doing train related things each year. Three 10-minute delays is only an extra 0.25%, or the equivalent of increasing the average wait time from 5 minutes to 5 minutes, 4 seconds. Marknoreply@blogger.com