Pandy's chart in DRF is still about as good as it gets.
http://www.drf.com/news/pandolfo-harness-par-times
If you're rating a shipper today from a different track in last, you'd adjust its last race time faster if shipping in from a slower track and vice versa.
Yonkers in last to Pokie today, = 1:57-2 -> 1:55-2 or a 2 second difference.