That speed sounds about right for I64, but remember to drop it to 20 mph for going through the tunnels. :mrgreen:
I've lived in HR almost all my life, and I have yet to figure out this phenomenon.
People slow down to 35 for the HRBT and MMBT where the speed limit is 55, but we speed up to 55 in the DT and MT where the speed limit is 35!
But I digress...
In general, I would say it is safe to do 9 over on the highways, and 4-6 over on the city roads. This can be bumped to about 15 over on I95 between Richmond and NoVA.