Road Pavement tie-in length

I don't know UK standards, but there is no single length. It's a function of prevailing speed.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

I agree with AC that it is a function of speed, but locally we also use a rule of thumb transition length for overlay projects milled into the existing pavement equal to a length of 1" of vertical overlay to 20' of horizontal length for the depth of the Hot Mix Asphalt Surface Course. The pay item typically used is Butt Joint (Sq Yd) or Cold Milling - Variable Depth (Sq Yd).

Thank you for your reply.