The Anonymous Widower

Mathematics Of The Lea Valley Lines

The mixture of Class 315 and Class 317 trains on the Lea Valley Lines are being replaced by new Class 710 trains.

Train For Train Replacement

London Overground currently has the following fleet, which work the Lea Valley Lines.

  • 17 x Class 315 trains – 75 mph
  • 8 x Class 317/7 trains – 100 mph
  • 6 x Class 317/8 trains – 100 mph

All these trains are being replaced by thirty-one Class 710 trains, which are 100 mph trains with a shorter dwell time at stations.

Time savings of over a minute, are claimed for each station stop, by other train manufacturers for their new generation of trains.

As one train is used on the Romford to Upminster Line, that leaves thirty trains to work from Liverpool Street to Cheshunt, Chingford and Enfield Town stations.

The Current Lea Valley Services

The current Lea Valley services can be considered to be two separate four trains per hour (tph) services to the following destinations.

  • Chingford
  • Edmonton Green with 2 tph extended to each of Cheshunt and Enfield Town.

Journey times are as follows from Liverpool Street.

  • Cheshunt – 39 minutes
  • Chingford – 27 minutes
  • Ednonton Green – 31 minutes
  • Enfield Town – 34 minutes

As an illustration of the slowness of some of these times, the fastest Cheshunt services take around twenty-five minutes, but they use the West Anglia Main Line, which has a higher speed limit.

Improving Journey Times

So how can journey times be improved?

The following factors will apply.

The Aventra Advantage

The Aventra and other modern trains will have the following advantages.

  • 100 mph operating speed.
  • Powerful acceleration and smooth regenerative braking.
  • Driver assistance systems to optimise train speed.
  • Level access from train to platform.

The last three factors will minimise the dwell time, when stopping at a station. Savings of up to three minutes have been claimed by some train manufacturers.

All Passenger Trains On The Routes Will Be Aventras

How much time this will save will probably be decided in practice.

Track, Station And Signalling Improvements

The operating speed of the routes is 40-75 mph , which could surely be improved.

Obvious problems include.

  • Level crossings at Bush Hill Park, Highams Park and Theobalds Grove.
  • Platform-train interface.
  • Provision of Harrington Humps.

A detailed analysis will probably be done to iron out any small time delays in running the routes.

Rewrite The Timetables For Aventras

Currently, the timetables are written so that they can be reliably run by the 75 mph Class 315 trains and also to allow for their possible presence on the routes.

How Much Can Be Saved?

This is a bit like asking how long is a piece of string, but assuming savings of a minute a station gives the following times.

  • Cheshunt – 24 minutes
  • Chingford – 20 minutes
  • Ednonton Green – 20 minutes
  • Enfield Town – 21 minutes

I would not be surprised if substantial time savings could be saved,

Liverpool Street Station

The pair of four tph services will mean that there will be a train arriving in Liverpool Street station every seven and a half minutes.

This should be no problem on two platforms, especially as all trains will be identical and designed for a fast turn-round.

Will they arrive and depart from a pair of platforms at Liverpool Street stations, like 2/3 or 4/5, so that passengers would know that their Lea Valley Line train always left from the same gates at the station?

This would surely make it easier for the train presentation teams!

Hopefully, by analysing the turning of trains, minutes can be saved.

Each Route In Detail

 

I shall now look at each individual route.

Liverpool Street To Edmonton Green

North of Hackney Downs station, in the Off Peak, the only trains on the route will be the following services.

  • Two tph between Liverpool Street and Cheshunt
  • Two tph between Liverpool Street and Enfield Town

These will be augmented in the Peak by some Greater Anglia limited-stop services stopping at Edmonton Green, Seven Sisters and Hackney Downs stations.

Current timings on this route are.

  • London Overground – 31 minutes with eleven stops using a 75 mph Class 315 train.
  • Greater Anglia – 23 minutes with two stops using a 100 mph Class 317 train.

As the distance between Liverpool Street and Edmonton Green stations is 8.6 miles, these timings give speeds of 16.6 and 22.4 mph respectively.

The following will speed up services on this route.

  • All trains on the route will be 100 mph Aventras.
  • The performance of the Aventras
  • Track, station and signalling improvements.
  • Driver assistance systems.

I suspect that my initial crude estimate of twenty minutes between Liverpool Street and Edmonton Green will be high.

Cheshunt Services

North of Edmonton Green station, the only service on the route will be the two tph service between Liverpool Street and Cheshunt.

As the route between Edmonton Green and Cheshunt is only 5.5 miles long, with just three stops, I wonder if when combined with the time between Liverpool Street and Edmonton Green, that the round trip time  could be reduced to under an hour, including the turn-round at both ends.

The current two tph service takes a few minutes over an hour-and-a half for a round trip from Liverpool Street, so three trains will be needed to run the service.

But if it could be done in an hour, then only two trains would be needed.

This level of speed improvement may seem ambitious, but the next generation of trains appear to be being built with it in mind.

Chingford Services

If the Chingford trains can do the trip reliably in twenty minutes, this would mean that a train could do a round trip from Liverpool Street to Chingford in under an hour, whereas now they take nearly an hour-and-a-half.

This means that four tph from Liverpool Street to Chingford needs either of the following trains.

  • 4 x Class 710 trains
  • 6 x Class 315/317 trains.

I doubt London Overground will park the spare trains in a siding.

It might even be possible to increase the frequency between Liverpool Street and Chingford. But this would probably need the removal of the level crossing at Highams Park station.

Enfield Town Services

North of Edmonton Green station, the only service on the route will be the two tph service between Liverpool Street and Enfield Town.

This is likely to be a route, where the return trip to Liverpool Street could be under an hour.

This means that two tph from Liverpool Street to Enfield Town needs the following trains.

  • 2 x Class 710 trains
  • 3 x Class 315/317 trains.

Conclusion

It does appear that on a rough look, the number of trains required to provide the current service will be less.

I think the three routes will need the following numbers of Class 710 trains to provide current services.

  • Cheshunt – 2 trains
  • Chingford – 4 trains
  • Enfield – 2 trains

As each train is usually eight-cars, then sixteen trains could be a minimum number to provide the current service.

But to do this, trains on each route must be able to do an out-and-back trip within an hour.

I think this could be possible and the extra trains will obviously be used to provide extra services.

 

 

 

 

 

 

 

September 25, 2017 - Posted by | Travel | , ,

1 Comment »

  1. Re Edmonton Green to Enfield Town: the Lincoln Road level crossing near Bush Hill Park is no longer an issue. It was closed to vehicular (but not pedestrian) traffic several years ago for safety reasons.

    Comment by Gordon Jury | September 25, 2017 | Reply


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