The lane width of a mobility corridor is 13-ft. The number of lanes required to accommodate the anticipated design year traffic is determined by the level of service evaluation as discussed in the .

The minimum shoulder width of a mobility corridor is 12-ft. This width applies to both inside and outside shoulders, regardless of the number of mainlanes. Shoulders must be continuously surfaced and be maintained.

Multilane divided pavements must be inclined in the same direction. The recommended pavement cross slope is 2 percent. Shoulders should be sloped sufficiently to drain surface water but not to an extent that safety concerns are created for vehicular use.

To facilitate pavement drainage, highways with three or more lanes inclined in the same direction should have an increasing cross slope as the distance from the crown line increases. In these cases, the first two lanes adjacent to the crown line may be sloped flatter than normal – typically at 1.5 percent but not less than 1 percent. The cross slope of each successive pair of lanes (or single lane if it is the outside lane) outward from the crown should be increased by 0.5 to 1 percent from the cross slope of the adjacent lane. A cross slope should not exceed 3 percent on a tangent alignment unless there are three or more lanes in one direction of travel.

Bridge structures with three or more lanes in one direction should maintain a constant slope of 2.5 percent, transitioning before and after the bridge accordingly.

Guidance on Vertical Clearance is presented in .

Stopping sight distance for mobility corridors is calculated using Perception-Reaction Distance and Deceleration Distance. The calculated and design distances are shown in . Significant changes from level grade may affect deceleration distance. Adjustment factors can be found in .

Undesirable speed differentials between vehicle types suggest that limiting the rate and length of the grades should be considered. Passenger vehicles are not significantly affected by grades as steep as 3 percent, regardless of initial speed. Grades above 2 percent may affect truck traffic depending on length of grade.

summarizes the maximum grade controls in terms of design speed.

shows the maximum allowable side friction factors and assumed running speeds for design speeds from 85-mph to 100-mph. The maximum side friction force is only realized at full superelevation and should be avoided unless conditions where limited space places constraints on the horizontal geometry allow no other options. These maximum side forces may be allowed for temporary traffic control during construction or maintenance.

and show minimum superelevation rates of various radii and design speeds for an e

max

of 6 percent and 8 percent, respectively. For multi-lane facilities, particularly where wide medians are used,

the radius applies to the innermost travel lane.

Desirable design values for length of superelevation transition are based on a given maximum relative gradient between profiles of the edge of traveled way and the axis of rotation. shows recommended maximum relative gradient values. Transition length on this basis is directly proportional to the total superelevation, which is the product of the lane width and the change in the cross slope. For superelevation on bridge structures, it is preferred to begin/end superelevation transition at a bridge bent line.

Vertical curves create a gradual transition between different grades which is essential for the safe and efficient operation of a roadway. The lengths of both crest and sag vertical curves are controlled by the available sight distance.

Vertical curves are required for all grade breaks on mobility corridors.

Minimum K-values are calculated using the same equations as in . Design Ks for both crest and sag vertical curves are shown in .

The length of a sag vertical curve that satisfies the driver comfort criteria is 60 percent of the sag vertical curve length required by the sight distance control. Driver comfort control should be reserved for special use and where continuous lighting systems are in place.