Re: Exhibition Street Bridge and City Link

[John Dennis <jdennis@acslink.net.au>]

>With regard to City link the problem is that there is not enough time for the
>system to scan the car send the info off, process it and send it back.  The
>scanning of the car works, the getting information on the car (like money left,
>number plate etc) works and sending the data back works.  The major problem is
>by the time it has done all this the car has gone.  It all takes too long to
>process.  The system is designed for speeds of around 40 km/h for time to 
>process everything, it just doesn't have the time (around 1 second) to 
>process everything at 100 km/h.  

That is effectively true.  My understanding is this...

The original system (from somewhere in Canberra, maybe) was designed
to simply acknowledge the transponder passing underneath the reader.
That can all be done locally, with no network traffic.

 Citylink's requirements mean that as each vehicle is "read", a
central database must be interrogated so that the transponder can give
the necessary number of beeps.  

I am not certain about "designed for 40 km/h" as the simple
acknowledgment works well at high speed - it is the end-to-end time
getting from the readers to the central machine and back which cause
the problems.

Cheers...JD
==========================================================
John Dennis                         jdennis@acslink.net.au
Melbourne                                  denjo02@cai.com
Australia                   Home of the Dutton Bay Tramway
DBT URL:       http://www.acslink.net.au/~jdennis/dbt.html