Level crossings and vehicle height

[pethadine82]

Just a quick question, what happens to the OHL when there is a level crossing?
Say if there was a lorry or a bus and it hit the line, it could be very dangerous.

Or if the level crossing section had the OHL omitted and the train was travelling slowly it would get gapped.

3rd rail trains don't suffer this as there are many shoes so at least one shoe will be in contact with the third rail thus feeding the rest of the system.
On a class 91 or EMU which are 4 car there is only one pantograph.

 

[scotraildriver]

The minimum height for the overhead line is 18feet 4.5inches. Higher than any bus or hgv, although abnormal loads or vehicles are required to check their height. If the hit it then it goes bang.

 

[asylumxl]

To add to this, the height can be altered dependent on the situation. I believe some bridges hve electrification lower than the above figure when needed.

I imagine when there is a high likelihood of taller vehicles passing over a crossing, that the height of the OHLE would be higher than usual to accomodate.

 

[L&Y Robert]

I remember when overheads were first appearing, at farm crossings and the like there were little catenaries on each side of the line above the boundary gates with a line of little bells hanging from it. So the farmer, hauling the elevator, let's say, strikes the line o' bells rather than the 25,000 volts (or whatever it is).

 

[ainsworth74]

I remember when overheads were first appearing, at farm crossings and the like there were little catenaries on each side of the line above the boundary gates with a line of little bells hanging from it. So the farmer, hauling the elevator, let's say, strikes the line o' bells rather than the 25,000 volts (or whatever it is).

They can still be seen in some places, the one that springs to mind is the level crossings just north of Doncaster station.

 

[455driver]

The height of the contact wire varies quite a bit depending on the local conditions.
Have a look at some pictures of a train with a pantograph going over a level crossing, the panto will be almost fully extended upwards because the wires are as high as they can possibly be, then look at some pictures of some trains going under bridges, the panto will be almost fully compressed and only just be above the train roof.

 

[snowball]

Where a bridge is built over the line to replace a level crossing on an electrified line, it may have to be higher than other bridges, because it has to clear the wires which are high for the crossing.

 

[DownSouth]

Where a bridge is built over the line to replace a level crossing on an electrified line, it may have to be higher than other bridges, because it has to clear the wires which are high for the crossing.

No!

Once the level crossing is closed, the wires can be returned to standard height (or lower than standard height for use with a compressed pantograph) and the replacement bridge built no higher than it needs to be to remain future-proofed against the potential introduction of bi-level passenger rolling stock and full-size freight.

Sure, it adds a little bit of extra work to modify the electrification, but that's pocket change compared to the cost of building a taller bridge purely to avoid the wires' previous height. Remember that the cost of constructing a bridge has an exponential relationship to height, not a proportionate one.

 

[Tomnick]

No!

Possibly no, probably yes!

In most cases, the level crossing can't be closed until the replacement bridge is completed. Exceptions are few and far between - I think one example (from a recent thread on here) involved the work around Joan Croft Jn, north of Doncaster, where it wasn't possible (and/or desirable) to construct a new bridge with sufficient height to clear the existing OHLE, which itself was high because of an adjacent crossing. In that case, they were able to close the crossing (presumably low usage and a reasonably convenient alternative) before the bridge was opened, but that's unusual!

 

[snowball]

Possibly no, probably yes!

That's why I said "may".

 

[Tomnick]

I know, I was responding to DownSouth's implication that a crossing could always be closed before construction of its replacement had even started - possible in a small minority of cases, but not otherwise!

 

[snowball]

Sorry, my last comment wasn't addressed to you! I was trying to reinforce what you said.

 

[scotraildriver]

The minimum height for the overhead line is 18feet 4.5inches. Higher than any bus or hgv, although abnormal loads or vehicles are required to check their height. If the hit it then it goes bang.

I meant that is the height at level crossings. Its much less than that elsewhere

 

[PermitToTravel]

There should always be signage before a level crossing (like here) indicating the maximum safe height - this even applies when the maximum safe height is greater than the standard clearance for height restrictions on the highway.

In practice, anyone driving a vehicle over 16'+6" tall will have checked their route beforehand (and possibly notified all the highway authorities along the route), as any bridges taller than that wouldn't have height restriction signs.

 

[snowball]

In practice, anyone driving a vehicle over 16'+6" tall will have checked their route beforehand (and possibly notified all the highway authorities along the route), as any bridges taller than that wouldn't have height restriction signs.

Perhaps not if it's a farm vehicle loaded with hay.

 

[High Dyke]

I remember when overheads were first appearing, at farm crossings and the like there were little catenaries on each side of the line above the boundary gates with a line of little bells hanging from it. So the farmer, hauling the elevator, let's say, strikes the line o' bells rather than the 25,000 volts (or whatever it is).

They can still be seen in some places, the one that springs to mind is the level crossings just north of Doncaster station.

Some public roads too. There's a set at Bathley near Newark. Not that it stops 'em some times... The most common problem being the vehicle driver that has fitted a larger aerial on the roof of the vehicle.