How does capacity change with speed?

[EM2]

Not au fait with Braintree, but i'll guess its one train in section? What are they assuming as the turnaround at each end? 9 minutes as now? What is the plan with the LCs, as they appear to put a spanner in it? I take it no new infrastructure is to be built and this is cheap as chips? The distances between the stations means that you aren't going to get a lot, if anything, from linespeed to be honest. They need to look at the Witham end and the 10mph to start with IMO.

I was discussing this with my colleague on night shift this week, and I think he said they're assuming a four-minute turnaround.
It is one train in section at the moment, but from the brief he's been given it looks like they want to go to two.
He's been given an outline of four suggestions:

1. New platform at Braintree
2. New platform at Witham
3. Increase in line speed
4. Installation of a loop

and from just having a chat with him, he reckons he'd plump for the loop. But he needs to put something in for the line speed bit.
My knowledge of track geometry is very limited, I suppose it'd be things like easing radii and increasing cant?

 

[Taunton]

Road vehicle maximum throughput per hour when not otherwise restricted (eg by junctions) is at 38 mph. This was determined by experiment a generation or more ago, and only with cars; it appears in road engineers' textbooks. Both above and below this speed throughput falls off. If you think about it, road vehicles are a sort of continuously moving block, managed by the driver following's perception.

Although some will write facetiously about car drivers having poor habits, in about 99.9999% of cases where they follow another they manage to do so without colliding with the one in front.

As described above, factors other than cruising speed, such as junctions, stops, etc, are much more significant to capacity.

 

[43074]

I was discussing this with my colleague on night shift this week, and I think he said they're assuming a four-minute turnaround.
It is one train in section at the moment, but from the brief he's been given it looks like they want to go to two.
He's been given an outline of four suggestions:

1. New platform at Braintree
2. New platform at Witham
3. Increase in line speed
4. Installation of a loop

and from just having a chat with him, he reckons he'd plump for the loop. But he needs to put something in for the line speed bit.
My knowledge of track geometry is very limited, I suppose it'd be things like easing radii and increasing cant?

Interesting, would removing stops at Cressing or White Notley achieve anything? Perhaps a skip-stop pattern, so for 2tph you'd have one train per hour calling White Notley, Braintree Freeport & Braintree and the other calling Cressing, Braintree Freeport & Braintree? So White Notley & Cressing retain an hourly service but at the expense of journey opportunities between the two. I can't imagine there's a very big market for White Notley - Cressing compared to journeys from Braintree to Witham, Chelmsford or London anyway.

 

[The Planner]

4 minute turnaround on a London train? Bit iffy... would agree with 43074, skip stop or fast second train might get somewhere but you would have to sort the crossings. Not sure an extra platform at Braintree would help as if the incoming is late then the outgoing has to wait.

 

[NSEFAN]

I was discussing this with my colleague on night shift this week, and I think he said they're assuming a four-minute turnaround.
It is one train in section at the moment, but from the brief he's been given it looks like they want to go to two.
He's been given an outline of four suggestions:

New platform at Braintree
New platform at Witham
Increase in line speed
Installation of a loop

and from just having a chat with him, he reckons he'd plump for the loop. But he needs to put something in for the line speed bit.
My knowledge of track geometry is very limited, I suppose it'd be things like easing radii and increasing cant?

Installing a loop is probably the best way to increase capacity and go from an hourly to a half-hourly service. The loop would probably best be located at White Notley as this seems to be half-way along the line, journey time wise.

Unless you can double the average speed and half the average journey time, increasing the speed alone won't get you from hourly to half-hourly. You could of course do what the St Albans Abbey line does and have a non-clock face timetable, but this might require the removal of through trains to London.