I've started doing that after nearly getting myself killed crossing the A45 between Coventry and Birmingham. On my 1:50,000 OS map it looked perfectly doable but in reality when I got there I could see that
the crossing point on the dual carriageway had been closed off with an Armco barrier. I could see why - it must have been lethally dangerous with large volumes of high speed traffic from both directions. I got there in the rush hour and it took me about 15 minutes to run across with my bike.
(The satellite picture I linked to must have been taken at a quieter time of day. When I was there, the traffic flow was relentless.)