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the other day i was coming back from San diego to los angeles, i was in the rear car (cab car of the surfliners). looking to the right where the cab is, the majority of the fast running was between 92 and 96 mph. The limit is 90 on the san diego line, would not have this triggered a brake penalty? Many times it was at a steady 95, and in 79 mph territory, it was saying 84. Are they off by 5 mph?
Eric Member # 674
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I don't know much about them, except that it is the engineer's job to verify the speedometer's reading is accurate as soon as possible. It is most-likely against the rules for a speedometer to be off by as much as 5 MPH. If the engineers are caught going only 3 MPH over the limit, they could get their licenses suspended for an X amount of time. So I can't explain your trip's speedometer!
Amtrak207 Member # 1307
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I believe the spec for engines manufactured after 1980 was plus or minus four mph, and yes, every engineer is required to clock their speedometer. If the cab car speedo was off by two or three and the engine was slow by its allowed four, that can make the difference you refer to. Also note that trains do not hold speed over varying grades and don't have cruise control, making the speed difficult to keep constant at times. Next time listen to a scanner if there are defect detectors in your area that broadcast the train speed. What I heard happens: first time you have a happy little chat with your road foreman, the second time you take a hike. This process may vary from one railroad to another.
------------------ F40PH #757099-8 March 29, 1976-November 18, 2001 P42DC #53063 November 18, 2001-???
Eric Member # 674
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Actually, Amtrak's P42's have a cruise control feature, but for "hogbacks" (a series of up-and-down areas of terrain), I don't know how well this would work, as throttle and air/dynamics would have to be continuously adjusted.
rms492 Member # 78
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thanks for the help, this has boggled me, also I forgot to mention that along san clemente (the beach section), I know the limit is 40, but again this speedo was at a steady 45, 5 mph more.
If anyone is coming back from san diego to los angeles, sit at the very rear of the last car and check the speedo. in the cab car of the surfliners.
Amtrak207 Member # 1307
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Ah, here it is. "The FRA regulations at 49 CFR 229.117(1) require that a locomotive built since December 31, 1980 , be equipped with a speed indicator that is accurate to within +/- 3 mph for speeds of 10-30 mph and +/- 5 mph for speeds in excess of 30 mph.
------------------ F40PH #757099-8 March 29, 1976-November 18, 2001 P42DC #53063 November 18, 2001-???
locomotiveguy Member # 1445
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The engine speed inicator on a P-40, P-42 is very accurate. If the wheel size on the cab car was not set, it's speed can be way off. The engine wheel size is checked every day. This cab car was probably treated as a car and has not been set in awhile. as the wheels get smaller the speed goes up.
cajon Member # 40
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On the Surfliners the cab cars are in the lead LAX-SAN & LAX-GTA or SLO. So they are used 1/2 of every R/T. All the engineers just know the speed indicator peculiarities of each cab car & engine & adjust accordingly.
locomotiveguy Member # 1445
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And some of them know how to, and do play with the wheel size setting, so they can go faster. Baaaad!
vthokie Member # 1456
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I suspect that the speedometers in trains tend to be off a little at times. I have a hand held GPS device that very accurately measures speed, and I've been as high as 86 mph briefly on a NJ Transit train where the speed limit is 80. I've also hit 105 mph on NJ Transit between Princeton Junction and New Brunswick (limit 100), and I've hit 129 mph on an Amfleet train pulled by an AEM-7. I haven't exceeded 150 mph on the Acela Express, though - they seem to max out at exactly 150.
IronPirate Member # 1476
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Wheel size is the main problem with speedometers being off. Also, on the P40,P42's, there have been a lot of problems with the sensor vibrating loose. The speedometers can bounce in large increments while holding a steady speed. It's the engineers responsibility to time a mesured mile and operate accordingly. An example: If I checked the speedometer and found that between a measured mile with the speedometer set on 79 mph, i got 45 seconds on a mile, then I am running 80 mph. Within guidelines I might add. However, if I got 51 seconds on that mile, then I'm only running 70 mph and I will adjust my train speed accordingly. I would have to note the descrepancy on the proper form on the locomotive.
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