The route starts in the Durban Central Business District. For the first few kilometres of its length, it runs parallel to the N3 on both sides as King Ndinuzulu Road North and King Ndinuzulu Road South (former Berea Road). At the Tollgate Bridge, it then turns to the south and passes through Mayville, before crossing under the N3 and passing through Sherwood.
At 45th Cutting, the route becomes a dual-carriageway freeway for the rest of its length. The route passes over the N2 (providing no access to it), and passes through Westville and Cowies Hill. The route then briefly touches the N3 at the Paradise Valley interchange, before passing through Pinetown.
After Pinetown, the route goes up Field's Hill, a 3km 1:15 gradient (this section is notorious for heavy vehicle accidents that can close an entire carriageway of the road). The route then passes through Kloof and Gillitts, before the R103 diverges, providing access to Hillcrest. The route then passes south of Hillcrest and through Assagay before merging with the N3, where it ends.
The route is roughly 35km long.
The M13 is the main thoroughfare to Durban for residents of Westville, Pinetown, Kloof, Gillitts and Hillcrest.
The M13 between the Paradise Valley interchange and its termination at the N3 used to be part of the N3 route until 1986, when the N3 was re-routed to pass south of Pinetown, Westmead and Winston Park. The M13 remains an alternative route to the N3, and is commonly used by motorists wishing to avoid the Mariannhill Toll Plaza, located on the N3 outside Westmead.