Long haul latency calculation?

["Christopher Wolff" <chris () bblabs com>]

Dear Nanog:

I was wondering if there is a benchmark for long-haul circuit latency...  For example if I had a T1 circuit with 2900 
miles between the two end-points (and assuming the provider is best case scenario) can I do something like 
(miles*latencyfactor) = 5 ms for 2900 miles?

Thanks,
Christopher