The road begins at a roundabout with the A418, the A4146 and the B440 south of Leighton Buzzard as a wide A-Class Primary Route.

The road passes through two roundabouts as a single carriageway, and acts as the Leighton Buzzard Bypass.

To enter Leighton Buzzard from the A505, an advisable route is to use the A4012 North from the roundabout at Billington.

Continue along the A505 along a 50 MPH stretch with speed cameras to reach the A5 at a roundabout, where the A5 (in the form of a spur) replaces its existing eastbound route to form the Dunstable Northern Bypass to M1 Junction 11a.

An east turn in Dunstable takes you to Luton on the secondary A class road, A505.

The road then enters Letchworth Garden City, though only the outskirts on the south side.

The recent construction of the Baldock bypass has created a dual carriageway from the A1(M) J9 through to Royston.

This piece of the road is not open to cyclists, farm traffic, motorcyclists under 50cc and has height and width restrictions.

The road passes a junction and dips into a large hill on the almost perfectly straight Dual Carriageway.

The road continues as single carriageway roughly north-easterly, following the ancient Icknield Way past Goffers knoll and passing through the hamlet of Flint Cross and over the Anglo-Saxon earthwork Bran Ditch.

Icknield Way bears off north to join the A11 whilst the A505 continues forward to Whittlesford, then another roundabout with a service station (BP) and the A1301, northbound to Sawston, The Shelfords and Cambridge, the southbound route goes to Saffron Walden and the Historic Chesterfords where the Icknield Way once ran.

The left lane is to access Cambridge, Haverhill and Linton on the A1307, and the right lane for A11 routes to Norwich and Thetford and A14 routes EAST to Newmarket, Bury St Edmunds, Ipswich and Felixstowe.

It also shares its route with the A5 near Dunstable and the A1081 near Luton Airport (grid reference TL 110 206).

The rest of the route was originally designated the A601 to the A11, but was extended west to Wing Hill, near Linslade, when the Leighton Buzzard bypass was built.