On Sun, 09 Nov 2003 12:02:49 +0000, Huge wrote:

Paul Weaver writes:
On Sun, 09 Nov 2003 11:18:08 +0000, derek wrote:
Oh, but it does. Very few cities in the world have a PT network on the
scale of London, combined with a horrific traffic problem for cars. If

And here lies the problem. Most PT supporters live in London, and don't
realise how lucky they Are to Have such a reliable and extensive PT
network.

Reliable?

In comparison to other towns and cities

"JNugent" wrote in message
...
wrote:

"Nick Finnigan" wrote:

"iantheengineer" wrote:

"Nick Finnigan" wrote:

but what would
you expect the maximum PT throughput per lane to be?

Per lane the maximum throughput of a lane for buses is 900 vehicles
per hour. This is purely a lane capacity in pcu (passenger car
units) that relates a bus to equal 2 passnger car units. An average
lane has a capacity of 1800 pcu, although this depends upon width
gradient and alignment.

But if they have to stop to pick up customers,
what is the achieved passenger throughput?

You cant really say this globally as it depends upon the density of
stops, the number of people alighting etc.

Fair enough.

Its got to be higher than the car figure at any rate as the car lane
capacity is 1800 pcu so thats 1800 cars per hour at say 2 people per
car (that is very generous!) giving 3600 persons per hour. Say a bus
achieved 1/3 capacity of 72 sealts ie 24, and they have a lane
capacity of 900 buses per hour you are talking 21600 passenger
throughput, taking out say 15 minutes of the hour to be ultra
generous to the car argument you are looking at 16200 which is far in
excess of the 3600 car argument, and I have been generous to the car
argument and have taken a pessimistic view of the buses.

That isn't right. That a bus lane could handle 900 buses an hour may be
theoretically possible, but there is no highway in the UK (probably in the
world) which carries 900 buses or bus movements an hour - probably nowhere
near that many in a *day* (where I live, which is on a bus rouite, it
doesn't approach that figure in a week). So you are being very optimistic
in
the case of buses, and not pessimistic at all.



If you read the earlier posts it is theoretical, the question asked was how
many buses *could* you get through a lane.

"Nick Finnigan" wrote in message
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"iantheengineer" wrote in message
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"Nick Finnigan" wrote in message
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"iantheengineer" wrote in message
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"Nick Finnigan" wrote in message
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Well, I hadn't mentioned throughput, but what would
you expect the maximum PT throughput per lane to be?

But if they have to stop to pick up customers,
what is the achieved passenger throughput?

You cant really say this globally as it depends upon the density of
stops,
the number of people alighting etc.

You are free to choose the optimal density of stops,
but please explain what that is. For simplicity, I would
go with your assumption that everyone alights at the
city-centre bus-station near their office.

. Say a bus achieved
1/3 capacity of 72 sealts ie 24, and they have a lane capacity of 900
buses
per hour you are talking 21600 passenger throughput, taking out say 15
minutes of the hour

Even at a bus every 5 seconds I don't see how you
can pick up any passengers; if any bus actually stops,
all the following buses would have to.






The same argument can be used for any mode though if a single lane with no
overtaking is installed as all traffic will be delayed due to stops by any
vehicle. This is why we have bus laybys in many places to prevent this.You
could argue that the car is less effective at this as it stops and can only
let a maximum of 4 people off before resuming the journey. A bus stops in
only a slightly longer timestep and can let a maximum of 72 people depart,
before it can set off So effectively you have the stop the depart and the
set off elements to measure. The stopping and departing are going to be
similar with a couple of extra seconds for the bus, but the efficiency of
the stop is far greater allowing a greater passenger per second exit ratio.

It is known that the bus service always seems to operate on no buses for
ages then a fleet come along at once and this is due to the fact that people
alighting on the first bus delay it so that the headway between it and the
following bus reduces, and so on until the first bus is full and perhaps
skips a few stops, and then the second bus will take over until the first
bus is able to stop again. But if the system were saturated the first bus
would load up and set off then the second would load up and set off and so
on, and the headways would remain overall similar with smaller variation.

"Ian Henden" wrote in message
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"iantheengineer" wrote in message
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"Nick Finnigan" wrote in message
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"iantheengineer" wrote in message
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"Nick Finnigan" wrote in message
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"iantheengineer" wrote in message
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To continue to build roads will continue the problem. The answer
is
puvblic
transport, but public transport cannot cater for all journeys
and
therefore
over time journeys will need to become more corridored. For
example
go
into
any city during the am peak and the tidality of the flow is
there
to
be
seen. IF we were to get all of the people from their cars onto
public
transport, or even better living nearer to the workplace, the
congestion
would be far less.

cars. Without cars on the urban road network public transport
would
be
faster and more reliable.

How fast would urban public transport be with no cars
on the road? (and no vans, cycles, taxis etc. if that helps).

Is this a question, is it not obvious enough.

It will be exactly the travel time + the stops for pick up/drop off,
without
any delay occurring due to congestion,

And what will the travel speed be, and who long will
each stop take, and how frequently will the stops occur?
Or, alternatively, how fast would a typical journey be?




Well this depends upon the usage the frequency of buses, the congestion
levels. The reason for the introduction of bus lanes at intersections
was
to
advance the bus to the front of the queues thus gaining back on the
journey
speed to make up for stops.

And the bus lanes are useless, because they are full of prats in cars
queuing to turn left or go straight on at the lights....





They are only useless if abused, many local authorities are now introducing
cameras on buses to poilce the abuse. If bus lanes are clear as they are
supposed to be then they do work.

"Paul Weaver" wrote in message
news
On Sun, 09 Nov 2003 14:04:55 +0000, Ian Henden wrote:
And the bus lanes are useless, because they are full of prats in cars
queuing to turn left or go straight on at the lights....

TBH I hardly see cars in bus lanes, they are usually just empty lanes.

Yep and so they should be and eventually when we all get fed up with sitting
at the lights in a a mile long queue as the bus sails by on the inside lane
we may start to think, how about taking the bus. If all the people that
could use buses used buses everyone else who couldnt would have an easier
time of it, but we have this mentality were we all *need* our car and cant
possibly use PT or a sustainable transport mode.

To commute is to waste, in both time and resources, the more we
reduce commuting the easier it will be for the people who have
to travel to get around.

True. Nobody likes commuting to work, I'd rather not have to do it. But with
the way the job market is these days, I can't just keep moving house every
time I change jobs, or I'd never get the chance to settle down anywhere.

We cant travel if the rate of increase in traffic continues

Traffic has only increased at the same rate as the number of driving license
holders has increased - due largely to women getting their own cars more
these days.

Once the number of license holders flattens out (which it will in due
course), traffic should stop increasing so fast. If we built a decent road
network now, it might be able to serve us forever.

Speed humps slow drivers down thus making accidents less likely and
less severe.

Not necessarily - they slow down for each hump and speed up in between - so
they may well be going faster in between the humps than they would be if the
humps weren't there.

As for speed limit in force at all times well if it wasnmt drivers would
get
confused, and is travelling at 20 over that distance such a problem??.

But as it's the school run parents who are usually the ones responsible for
speeding outside schools, surely having a 24/7 20-limit is wasteful and
unnecessary?

On Sun, 9 Nov 2003 15:50:32 -0000, "iantheengineer"
wrote:

It is known that the bus service always seems to operate on no buses for
ages then a fleet come along at once and this is due to the fact that people
alighting on the first bus delay it so that the headway between it and the
following bus reduces, and so on until the first bus is full and perhaps
skips a few stops, and then the second bus will take over until the first
bus is able to stop again. But if the system were saturated the first bus
would load up and set off then the second would load up and set off and so
on, and the headways would remain overall similar with smaller variation.

It's much more boarding (and ticket sales) rather than alighting that
causes this problem; if off-bus ticketing were the norm (outside
London), and all buses larger than van-derived minibuses were fitted
with two sets of doors, this would be significantly reduced.

Neil

--
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Try my first name at the above domain instead if you want to e-mail me.

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