On Fri, 11 Apr 2008 13:54:58 -0700 (PDT), Mr Thant
wrote:

On 11 Apr, 19:04, Tom Anderson wrote:
Provided that the bus can get good GPS and GPRS signals. GPS is
notoriously inaccurate in built-up areas, as buildings block lines of
sight to the satellites, and introduce reflections which confuse the
receiver (like ghosting on the telly). I wonder what they're doing to deal
with this?

I've read a TfL paper that I can't find right now that found it to be
surprisingly accurate, something like dead on 98% of the time.
Presumably to do with being aerial mounting a large antenna on the bus
roof where it has a good view of the sky, rather than the tiny
internal one in consumer gear that gets blocked by the car roof.

My general experience of I-Bus has been good even though my route runs
out of the first garage equipped with it so we've had all the bugs and
changes to contend with. There is still the odd bus with non functioning
displays or visual but no audible (or vice versa) announcements. Only
twice has something really silly happened - the first was leaving Wood
Green and I-Bus believing we were still heading there. Even when we
passed ourselves going the other way (IYSWIM) the system did not correct
itself. The other was the system seeming to be completely dead and then
suddenly springing into life after leaving a stop. I have no idea how
GPS works but if it uses any form of cellular pattern to locate a
vehicle I did wonder if we had crossed from one cell to another in the
second example.

Is there a way to tell if a bus is using iBus data or Countdown. Have
any iBus-based displays even been deployed yet?

I-Bus equipped vehicles have a blue and yellow sticker in the
windscreen. There is also a console in the cab - typically just above
and to the right of the driver's head - and this shows the headway gap
and schedule "divergence" on a display to the driver.

I am not aware of a way of knowing if a bus is Countdown equipped as the
bus mounted kit is on the rear axle AIUI. This is one reason for the
unreliability of the system - hard to maintain and takes hours to fix
and means the bus is off the road. Not what an operator under a
performance based contract wants.

I am not aware that any Countdown displays have been integrated into the
I-Bus system yet - I think this part of the project is running late.
Certainly we have some local Countdown displays that are on I-Bus
equipped routes and I have not noticed any substantial change or
improvement to the data. There will be a further 2000 stop displays as
part of I-Bus but this phase is only just out to tender. I don't know if
it incorporates the integration of existing displays as part of the
scope or if it is simply the displays themselves and installation.

--
Paul C


Admits to working for London Underground!