In message , at 12:51:11 on Thu,
16 Mar 2006, John Rowland
remarked:
Also, computer-control of the entire system
means that if the vehicle in front is braking,
the one behind can react within a fraction of a second.

I would hope that the vehicle behind would start braking first, and only
when the brakes on that are known to be working would the vehicle in front
start braking.

That won't work, because by the time the hundred vehicles behind the
lead one have gone through that process, the first will be well past
whatever it was braking for.
--
Roland Perry

"Roland Perry" wrote in message
...
In message , at 12:51:11 on Thu,
16 Mar 2006, John Rowland
remarked:
Also, computer-control of the entire system
means that if the vehicle in front is braking,
the one behind can react within a fraction of a second.

I would hope that the vehicle behind would start braking first, and only
when the brakes on that are known to be working would the vehicle in front
start braking.

That won't work, because by the time the hundred vehicles behind the lead
one have gone through that process, the first will be well past whatever
it was braking for.

No, because it will be braking for a station at which it has known for
several minutes that it would be stopping.

In article ,
John Rowland wrote:

"Roland Perry" wrote in message
...
In message , at 12:51:11 on Thu,
16 Mar 2006, John Rowland
remarked:
Also, computer-control of the entire system
means that if the vehicle in front is braking,
the one behind can react within a fraction of a second.

I would hope that the vehicle behind would start braking first, and only
when the brakes on that are known to be working would the vehicle in front
start braking.

That won't work, because by the time the hundred vehicles behind the lead
one have gone through that process, the first will be well past whatever
it was braking for.

No, because it will be braking for a station at which it has known for
several minutes that it would be stopping.

And this is going to work /how/ for child-in-front?

--
Andy Breen ~ Not speaking on behalf of the University of Wales, Aberystwyth

"Who dies with the most toys wins" (Gary Barnes)

In article ,
John Rowland wrote:
I would hope that the vehicle behind would start braking first, and only
when the brakes on that are known to be working would the vehicle in front
start braking.

Wouldn't that mean that if the brakes failed on any vehicle that no vehicle,
in front or behind it, would ever stop?

Dave
--
Email: MSN Messenger:

"John Rowland" wrote in message
...

I would hope that the vehicle behind would start braking first, and only
when the brakes on that are known to be working would the vehicle in front
start braking.

Why? At the maximum speed of 25mph with the minimum headway of 2 seconds
there will be 73 feet between pods. The highway code gives a stopping
distance of 75 feet for cars travelling at 30mph, however 30 feet of this is
the thinking time. With an electronic control system, this thinking time
could be considerably reduced.

Of note is that the highway code recommends two second headways for cars on
the road.

http://www.highwaycode.gov.uk/09.htm#105

--
Ronnie
--
www.greatcentralrailway.com
Adjust the farmyard animals before replying

"Andrew Robert Breen" wrote

And this is going to work /how/ for child-in-front?

I'm alweays slightly apprehensiver if I'm riding in the front of a DLR
train - what do I do if I see an obstruction ahead, and the Train Captain is
checking tickets a good way back?

Peter

In message , John Rowland
writes

No, because it will be braking for a station at which it has known for
several minutes that it would be stopping.

You need to consider the case of an emergency stop - front car suddenly
halted by a seized wheel, lightning, crashing into a tree that has
fallen onto the guideway (and that hasn't been spotted by its own
forward sensors) etc.

AIUI, the computer system reacts to any such unexpected change of speed
with an emergency stop command to all vehicles. At the projected speeds
and headway, there is ample time for the car behind to stop before
hitting the halted vehicle.

--
Paul Terry

"mmellor" wrote:

ULTra pods are self (battery) powered, with no ability to couple
together. The theory is that the headway is as short as 2 or 3s, and
they recharge when stationary, awaiting the call.


You write about ULTra pods as though there are existing systems that
are carrying hundreds of thousands of people reliably, in comfort and
safely. If so, where can they be seen in full operation carrying
members of the public on a daily basis? Where can I ride on one?

Or is this just someone trying to float untried technology for an
extremely demanding application (one of the five busiest airports in
the world) on the basis of an unrepresentative small scale short term
trial in Cardiff, Wales?

In message , at 13:47:40 on Thu,
16 Mar 2006, John Rowland
remarked:
That won't work, because by the time the hundred vehicles behind the lead
one have gone through that process, the first will be well past whatever
it was braking for.

No, because it will be braking for a station at which it has known for
several minutes that it would be stopping.

It's more likely to be braking for a queue at the next station because
one of the pods a few dozen ahead has a little old lady with a very
heavy bag she can't unload easily. So it's not quite as predictable as
you suggest.
--
Roland Perry

Tom Anderson writes:

More importantly, they're presumably cleared for higher levels of jerk
and deceleration than trains - after all, the limits on train
maneuvering are regulatory ones related to passenger comfort and
safety, rather than engineering ones, right? If they have
forward-facing all-seater accomodation, such a difference would make
sense.

If a vehicle is going to deccelerate sharply, I'd rather be in a backwards
facing seat than a forwards one!

In fact, don't the seats in the end carriages on a Pendolino face
backwards (when leading) for this reason?

Adam