I have quite a bit of experience of big scalextric events. I used to run an annual "Drink and Drive" charity event. Had a 4 lane track and matching cars (VW beetles). At 1 point I owned several (scale) miles of track. I have only recently had a big clear out and got rid of load of it. Sorry!
A couple of top tips!
Have spare cars. You won't have time to fix the copper brades mid race.
Time your event and add it up. it's surprising how many races you will need and how long they take.
Have a master power switch to kill the track. best way to get people off after theri race finishes (see above)
If you can, supply each lane from it's own transformer. This stops the cars from stealing power from each other. The real pain with this is when a car comes off and stops stealing power! The other gets a boost and comes off as well. This means you get "close" races all the time and can cause trouble with scoring.
Use a computerised lap counter/timer if possible. I used to use one that was free on the net. You will need to build your own track detectors though. Putting one of these through a data projector looks really cool and keeps the attention of those who can't see over the heads at the track. Failing that, use a seperate human lap counter for each lane..
Finally;
When you are driving, the trick is to stay on. You lose much more time scrabbling to replace a car that you ever would by running a bit slower..
