Software Updates at the Humber Bridge

All my own work

One thing which I’m very proud of is that I helped to write the software that manages the toll data from the Humber Bridge. Ian and I wrote the “Instation and Control Room Mimic” system which tracks the traffic over the bridge, makes sure that vehicles are registered correctly by the toll booth operators and totalises all the takings. We wrote the programs around 12 years ago which means that if my code was a child it would now be starting secondary school. Scary stuff. (and probably due for an update)

Some time ago the wonderful Verity Stob introduced me to Meir M "Manny" Lehman's Software Uncertainty Principle. Put simply, it states that at some point in the lifetime of a project certain assumptions that were baked into the solution when it was first built become wrong. Today that happened to me. One of the assumptions that I’d made in the design was that it would never be free to cross the bridge. The program was built to validate the price entry and reject any values which were less than or equal to zero. And then at the weekend the Humber Bridge Tolls were revised downwards (a very nice thing to happen) and it became free for a motorbike to cross the bridge. Thing is, my software didn’t allow for this. And so, for the last day or so the price of a motorbike crossing the bridge has been recorded as a single penny (although of course the money wasn’t collected)

Today I drove round to the Bridge Control Room and did a code update of the bridge software, effectively changing a >0 to a >=0 and now the prices can be set correctly.

Comments

[Nceku Moyo]

Wow.... So what programming language is the software written in?

[jj]

That will have set them back a few thousand then Rob !!!

[Danny]

Client comes to you and asks for a minor revision.
Say "Hmmm, that's a lot of work"
Charge them loads of money and change one variable :P

Thats the Rob Miles way ;)

[Carl Pickering]

Just wait until the price goes up to £655.35

[Rob]

The software is written in Simatic:

http://www.automation.siemens.com/mcms/topics/en/simatic/Pages/Default.aspx

This is an industrial contol system written by Siemens. The actual procedures that implement the behaviours are all in C. It has the wonderful ability that you can update the code, on the fly, on a live system. Which is what we did today. Now I have to go back to my reference copy and apply the same updates. Actually there are a few changes that have been requested and we'll prepare a formal spec. via Seed Software.

When I come back from "holiday".