The B4506 runs over the Chiltern Hills in the counties of Bedfordshire, Buckinghamshire and Hertfordshire.
Starting in Northchurch, Berkhamsted on the A4251 (ex A41) at a 'give way' sign the B4506 soon crosses the Grand Union Canal at a narrow bridge and climbs to Northchurch Common. The road here is unfenced. The Chiltern Way is crossed and Ringshall reached. From here we are in Buckinghamshire.
Ringshall Road is descended under a 40mph speed restriction. A flat NSL run then follows to Dagnall and its roundabout. Bedfordshire is now entered and the road continues at the foot of the Dunstable Downs. The B4540 to the Zoo is passed and the road ends at a roundabout on Icknield Way (B489)
New Road bridge,Northchurch