The Highways Agency is announcing details of a a £175 million scheme to allow traffic to use the hard shoulder on one of the busiest sections of the M25.
Work is expected to start next year in Kent and Surrey.
But motoring groups say it's "a scheme on the cheap" and another lane should be built. They are also concerned there will be long delays while the work is carried out.
The work will take place between J5 (A21) near Sevenoaks and J7 (M23) the turning for Gatwick, a fifteen mile section of the road.
Members of the public can see the plans at a public exhibition from 1500 today (Friday) atNutfield Lodge, Nutfield Lane, Redhill, RG1 4ED