100andthirty
Member
Determining coasting points for each inter-station run is not particularly hard if you've got access to an engineering level train performance simulation model which London Underground has had in place for over 30 years - updated as computing advances of course. The process is something like this:
1) calculate the shortest possible run time between each station pair taking into account line speed, speed limits and gradients.
2) Determine by how much you want to extend the run time by coasting - the rule of thimb used to be 8 seconds per mile.
3) Redo the first calculation which might involve a little iteration to identify the best speed to initiate coasting.
Step 1) is always done anyway, so adding steps 2) and 3) is not a burden.
The notion of having a simple speed control was applied to D stock. This was, in fact slightly more complex to optimise than the regular coasting calculation as a single pair of speeds had to be found that approximated to 8-sec/mile across all the different inter-station sections. In the end two speed pairs were chosen, one for in town where speeds are low and the other out of town where speeds are higher. If trains were running late, coasting cold be cut out using a switch which displayed a green/white striped flag in the offside front windscreen.
The intent of coasting was to save energy for trains running to time by 'using up' the make up allowance provided in LU's working timetables. For automatic trains this only really works if the ATO system can control whether to coast or not on a train by train, section by section basis. The only line where this level of sophisitcation has been implemented is the Victoria line.
1) calculate the shortest possible run time between each station pair taking into account line speed, speed limits and gradients.
2) Determine by how much you want to extend the run time by coasting - the rule of thimb used to be 8 seconds per mile.
3) Redo the first calculation which might involve a little iteration to identify the best speed to initiate coasting.
Step 1) is always done anyway, so adding steps 2) and 3) is not a burden.
The notion of having a simple speed control was applied to D stock. This was, in fact slightly more complex to optimise than the regular coasting calculation as a single pair of speeds had to be found that approximated to 8-sec/mile across all the different inter-station sections. In the end two speed pairs were chosen, one for in town where speeds are low and the other out of town where speeds are higher. If trains were running late, coasting cold be cut out using a switch which displayed a green/white striped flag in the offside front windscreen.
The intent of coasting was to save energy for trains running to time by 'using up' the make up allowance provided in LU's working timetables. For automatic trains this only really works if the ATO system can control whether to coast or not on a train by train, section by section basis. The only line where this level of sophisitcation has been implemented is the Victoria line.
At the rate they are progressing I have confidence that there will still be some!!