Once a vehicle has left the pavement and traveled onto the unpaved or deteriorated shoulder, the presence of abrupt or vertical pavement edge drop-offs can make it difficult for a driver to safely re-enter the paved travel lane. Studies show that drivers tend to attempt to return immediately to the paved travel lane; in doing so, they tend to over steer when “scrubbing” (the intense rubbing of the right-side vehicle tires against the pavement edge) prevents the vehicle from climbing back onto the pavement.
Safety Edge is a relatively easy and inexpensive countermeasure to pavement edge drop-offs. It is a tapered transition between the paved surface and the unpaved shoulder. The recommended 32° ± 5° angle with the horizontal tapered pavement edge or fillet can help drivers make a smoother, more controlled reentry back onto the paved travel lane, compared to a more abrupt or vertical edge. The tapered edge helps prevent drivers from overcorrecting if they drift onto the shoulder, thus decreasing the likelihood of the vehicle crossing into opposing traffic or leaving the roadway. DelDOT incorporated the Safety Edge countermeasure into its standard paving practice in 2011.