With respect to new electronic
technology for information sensing, storage, and processing, railroad technology
has lagged behind that of aircraft and highway vehicles, but currently is
catching up. The role of the human operator in future rail systems is being
debated, since for some limited right-of-way trains (e.g., in airports) one can
argue that fully automatic control systems now perform safely and efficiently.
The train driver’s principal job is speed control (though there are many other
monitoring duties he must perform), and in a train this task is much more
difficult than in an automobile because of the huge inertia of the train — it
takes 2 to 3 km to stop a high-speed train. Speed limits are fixed at reduced
levels for curves, bridges, grade crossings, and densely populated areas, while
wayside signals temporarily command lower speeds if there is maintenance being
performed on the track, if there are poor environmental conditions such as rock
slides or deep snow, or especially if there is another train ahead. The driver
must obey all speed limits and get to the next station on time. Learning to maneuver
the train with its long time constants can take months, given that for the
speed control task the driver’s only input currently is an indication of
current speed.
The author’s laboratory has
proposed a new computer-based display which helps the driver anticipate the
future effects of current throttle and brake actions. This approach, based on a
dynamic model of the train, gives an instantaneous prediction of future train
position and speed based on current acceleration, so that speed can be plotted
on the display assuming the operator holds to current brake-throttle settings.
It also plots trajectories for
maximum emergency braking and maximum service braking. In addition, the
computer generates a speed trajectory which adheres at all (known) future speed
limits, gets to the next station on time, and minimizes fuel/energy.
