What market signals do you use to tell a horse race is about to go off?

[jamesedwards]

I'm running a Guardian automation that relays on being close to the off time of a horse race. Using start time for a horse race becomes less accurate during the day as things get delayed. What system/tells/market signals does anyone use to predict when close to off rather than simple start time?

[Euler]

You can really tell without looking at pictures.

The only thing I would say is that volume (per second or so) dies off fairly quickly after post time and will remain low before rising slightly again before the races is about to start. But some of this depends on what is going on elsewhere as well. So it's not perfect.

[Euler]

I tend to trade past post and convert orders to SP so even if the race starts late, the order will get matched anyhow. I check the inplay status to square things off when the race has started.

[Big Bad Barney]

How important is it to get it right/spot on? Just thoughts... would people pay for an API service for such a thing? (It'd have to be manually data entried by a watcher, etc)