It has always seemed to me that the 750 volt 3rd rail is a bad
idea. Rather it is the idea that somebody (Sprague?) first thought of
and it got made permanent. Its drawbacks in its present form seem to
me to be :-

* The possibility of electrocuting somebody. Are there many
casualties? More difficult to answer; how much do the procedures to
avoid electrocution cost in direct and indirect costs?

* It too often gets covered with ice in winter (and wet leaves
in autumn?)

* The danger of electrocution means that voltages cannot be
raised to increase power delivery. Italian state railways (FS =
Ferrovia della Stato) started with 3000 volt overhead wires, but
everything has now been done so that they can increase the voltage to
6000 volts, so doubling the power that can be delivered.

So I have been thinking of the possibilities of shielding the
3rd rail. The shield would be made of springy plastic, with square
holes moulded in the bottom, to allow rainwater and leaves to drop out
of the bottom and cooling air to rise through them. The holes would be
too small to allow a hand to be put through and too far for a finger
to reach the 3rd rail.

The shield would be fitted by springing open the shield, and
pushing it upwards over the bottom of the 3rd rail. A cut will have to
be made on the train side at each insulator to fit the shield, and
some of the bottom grille cut away to allow it to be put over the
insulator. Keys projecting into the inner space will be clipped to the
lower web of the rail, thus allowing air to flow round the 3rd rail.
This requires plastic which will keep its spring for many years, and
this might be a problem.

Along the side of the top there is a slot which the train
pick-up shoe (more like a "tongue") goes through. It is under an
overhang to stop rain and leaves from getting in, but being at the top
it creates some chimney effect for cooling the 3rd rail.

The slot at the top would be too narrow and too far from
the 3rd rail to put hand or finger onto it. Suicide will still be
possible for somebody who wants to do it, but somebody who is on a
railway track and wants to commit suicide has plenty of other ways of
bringing it all to an end. An ACCIDENT is now very difficult.

To complete this would obviously be a 10 or 20 year project,
(even longer to replace some of the longer-lived stock with higher
voltage stock) but some of the benefits, such as no icing in winter,
would come immediately. To get everything lined up it obviously also
requires a standard of track laying better than some we have seen in
recent years. Is that good or bad?

There are shielded 3rd rails on the continent, but I'm afraid
I can't see Network Rail, with its many problems, and its difficulties
with the TOCs, undertaking a project like this, no matter how
worthwhile.

Michael Bell



________________________________________
| ___________________________________ |
| | | |
| | ||||||||||||||||||||||||||||| | |
| | || ____ _______________ | |
|__| || | | | | | |
|| | | |_ _| | |
||||||||||||||||||||| | | | 3rd | | |
| | | rail | | |
Pick-up tongue | | | | | |
| | | | | |
| | | | | |
| | | | / |
| \ / \ / |
| \ / \ / |
| // \ |
| /____________________\ | Shield
| __\ /___ | clipped
| | | | to lower
| | | | web of
| | | | rail
| |___________________________| |
|_______________________________|

Plastic grille at bottom.