Trail Braking

Copyright ©2006 by Paul Niquette. All rights reserved.

The sketch below depicts a commuter train operating at some cruise speed vC behind another train.  To maintain safe separations between trains, the wayside control system detects the preceding train and transmits speed commands to the "train in trail."  The actual speed of the preceding train is not known, only the location of its rear-most car.   Headway, the time between successive trains passing a given point, is an important determinant of railroad performance (see Streetcar Mystery).

Which of the following operating speeds will permit the shortest headway?

(a) 50 miles per hour
(b) 60 miles per hour
(c) 70 miles per hour
(d) 80 miles per hour