>It is true enough, cylindrical wheels do seem to reduce hunting, but only if gauge tolerances are also tightened sufficient that both flange radii simultaneously contact the rails. But this causes very rapid wear, which soon enough negates any such benefit. And as the wear continues, the car not only hunts badly, but will sometimes slap side to side violently; because without the tapered tread, there is then no control at all until a now worn flange finally HITS a rail.

This exactly is what CalTrans found with their locomotive wheels, but Amtrak knows better.

>Moreover, as the British railways discovered through extensive research, some minor amount of oscillation is needed, to keep the rail and wheels clean enough for safety critical train detection to work reliably. As discussed below, cylindrical wheels did not allow enough of that - to BART's great detriment.

Interesting.

>I believe all railroads have had track circuit shunting issues at one time or another. -snip>But as for shunting problems in general, I believe BART has had way more than its share.

The incidences I was thinking of were occurring right about the time the line between MacArthur and Concord was opened for service. On first runs of the day, cars/trains would routinely fail to shunt the track circuits. An electrical engineer from Cal Berkeley told me that what had been happening was that between the last train of the night, approximately 12:30 AM, and the first train of the morning, approx 6 AM, the fog would condense on the rails, producing a light coating of rust. The railhead always looked clean and shiny, but if you wiped your hand on the surface of the railhead (that early in the morning) and looked at your hand, your palm would be coated with rusty moisture. It turned out that this oxide layer was acting as a ½ wave rectifier and preventing shunting. This lead to the wheel scrubbers, which were subsequently replaced by the SOR system (I think, and it's been a while . . . ).

I found it ironic that the BNSF's problems were attributable to the same sort of thing: oxidation caused by that nighttime pesticide spraying.

>So again, BART's Bechtel re-invention of the wheel has proven a great dis-service to it, and to the public which daily has to put up with and pay for BART's woes. All told, an across-the-board unmitigated disaster - actually!

B. S. Stokes at work (and play).