How to configure ISA 2006 failover?

We have 2 ISA 2006 servers, one is connected to one ISP (Internet Service Provide) while the other is configured for another ISP. If one ISP goes down,can the traffic be routed via the ISP which is still functional.

This is the first time I am posting a question, hence let me know if there is any specific detail that I have missed out

Thanks,
Milind