On 14 July, 01:09, Andy wrote:
On Jul 13, 11:41*pm, Jamie Thompson wrote:
Indeed, the loop would allow two trains at once, but there is really
no way to increase the frequency to every 30 mins without a loop. The
old timetable (in immediate post-electrification days) had a train
every 40 mins during the peak, but the time keeping fell off a bit
towards the end of the rush hour and there was a gap in service to
allow for this. Current frequency is a train every 42 mins at the
start of service, then 45 mins for most of the day but 45-50 mins in
the evening peak. The journey takes 16 mins end-to-end which doesn't
leave sufficient turn around times to run a reliable service every 40
mins (this would only allow 4 mins at each end).

Fair enough. The mighty wikipedia says the line speed varies between
40-75mph. Could raising this slightly not give the required layover
time...expensive I know, but we're already well off into fantasyville
here anyway. For the record, I think the loop's a great idea. I
wonder, would having 3 or 4 trains on the branch (you'd need both
termini to have dual platforms or at the very least pre-platform
loops) not work too? Two in motion, and one or two waiting at the
terminus/i for the next to arrive. Plenty of layover time.

But there is actually plenty of capacity off-peak to do this and
London Midland are planning have these relief services running from
Watford Junction anyway during the peaks anyway. If you look between
17.00 and 18.00 or between 18.00 and 19.00 there are currently 6
trains leaving Euston on the slow lines, add in the Southern service
and there are 7 passenger trains per peak hour leaving London. The
time penalty for the current Harrow / Bushey stoppers is 4 mins to
Watford Junction at non-peak times although often less during the peak
as many trains are Harrow or Bushey not both. For an easy example,
removing the Harrow and Bushey stops from the xx.04 and xx.34 off-peak
services would allow xx.10 and xx.40 services calling at Queens Park,
Wembley (ok the first two are 'extras'), Harrow, Bushey and Watford
Junction to run without impacting on the following service which uses
the slow lines (xx.24 and xx.54). Compared to many other routes out of
London, the WCML slow lines are not at capacity, even allowing for the
freight which runs during the peak. Platform loops don't really add
capacity whilst allowing for a reliable timetable, as there is a very
narrow slot for the fast train to run through whilst the slow is
stopped in the loop.

Is it really that hard to hold them to timetable? My main concern
would be the acceleration reducing capacity, but that could be
countered by making the loops longer. The Reason I first thought of
these loops was my experience of standing at Harrow & Wealdstone
during the peak with the platform being crush loaded and trying to
force my way back behind the yellow line when a ex-Bushey non-stopper
shot past. Incredibly dangerous, especially when you don't get the
warnings until the trains already shooting through - if indeed you can
hear them at all due to the crappy PA system. Strikes me that if you
put the platforms on loops the air shockwave would be non-existent and
you'd have less change of having your face ground against the side of
a 90mph train if someone happened to bump you by accident.

Also, it does seem that there is spare capacity, but then I wonder
about several peak gaps in service of half an hour or so (ok, 15
really, but it's 30 if you want to go to Euston rather than Clapham),
which made me wonder if I was missing something.

But you'll have the same stopping at Harrow and Bushey whatever train
run on the AC lines, as the existing service will have to retain their
calls. Currently the DC services have a 16 min turnaround at Watford
Junction which allows plenty of recovery time (and this is often
used). You would turn this into 4 mins at St. Albans for every other
train, with maybe a couple of mins stand at Watford Junction in each
direction to adsorb late running / power switch over when coming onto
or off the DC lines.

Sorry, I thought we were proposing additional calls? - My bad.

Current plans see 7 x class 321 units retained by LM (unit 411 and 412
have already been repainted in LM livery) and originally it was to be
10.

I stand informed and corrected

Another random thought, given the ample capacity on the DC lines, and
with a flyunder and a link to the MML/proposed Radlett freight
terminal, you could increase freight capacity to Wembley yard whilst
(depending on the location of said flyunder), possibly even moving
some freight off the slow lines between Watford and Wembley.