Roland Perry wrote:
In message , at 17:35:07 on Sun,
27 Jan 2013, Brian Watson remarked:
I found myself thinking, "why start at Shenfield?"

Is there so much demand on that line for such a route, or capacity further
up it (at Chelmsford for example)?

Shenfield is where the line stops being 4-track and splits into two
2-track lines (one to Southend the other to Chelmsford and beyond). As
well as being a junction, it's always been an important railhead and
interchange point. And the "town on the edge of London" although being a
couple of miles inside Essex.

Also the railway through Chelmsford, and the station itself, is on a brick
viaduct, which makes any additional trackwork required to turn back a
large number of trains somewhat impractical.

Well, yes, but the capacity from Southend and the Chelmsford direction is
(as you say) throttled and I'm wondering why the people beyond Shenfield are
suddenly going to get a great urge to travel to Maidenhead and beyond

They won't be. Maybe some as far as Heathrow, but the majority of Essex
travellers will be heading for central London.

Yes, the same as Thames Valley travellers, who may be going as far as
Canary Wharf or perhaps Stratford, but not out to Shenfield. It's just the
same as Tube routes that run through central London: hardly any normal pax
do end-to-end journeys.