lanes would be provided, clear of the normal traffic lanes, to permit traffic to slow down before entering the access drive and to pick up speed before weaving into the high-speed traffic stream on the toll road.
Access drives would lead by easy grades and curves past the toll booths which would be visible from the toll road and the intersecting road. Ample storage space for entering vehicles would be provided approaching the toll booths.
A typical grade separation, access roads, and toll booths for a twolane toll road are shown in plate 32. Traffic on the toll road should be prevented from making left turns. Two access drives and two toll booths, therefore, would be provided regardless of traffic density. To prevent all possible conflicts of turning traffic the toll road would have to be designed as a four-lane divided road at the intersection. A less complete facility, but one which might suffice on the more lightly traveled roads, would be provided by widening the two-lane road to three lanes, as shown in plate 32. The middle lane, in this case, should contrast in color and surface texture with the outside traffic lanes and generally would be used only by through traffic to pass vehicles slowing down to leave the toll road or vehicles just entering the toll road. Acceleration and deceleration lanes, therefore, would not be necessary with this type of facility.
As toll collection constitutes an appreciable operating expense, study was made of the possibility of utilizing only one toll booth at each access and providing traffic circulation so that all crossing of traffic would be avoided. The result is shown in plate 33. On a conservative basis it was estimated that the annual cost of operation of a second toll booth would be less than the excess of the annual interest and amortization charges on the cost of the extra grade separation structure and other additional construction over the relatively simple arrangement of two accesses. This is particularly marked for two-lane roads where the cost of constructing an appreciable length of four-lane divided road as against a three-lane road must be added to the extra cost.
At intersections with important existing highways on which the making of left turns is hazardous, four access roads or a full cloverleaf type of grade separation with four toll booths should be provided.
LIGHTING
The proposed roads would be lighted to the extent justified. Lighting is considered to be necessary in tunnels, on long bridges, and access drives and in suburban areas where lighting of adjacent streets would confuse drivers if similar lighting were not provided on the road. While fixed sources of light are generally to be preferred, other methods of outlining the road at night, such as the use of reflectors, may be considered as supplements and possibly as a substitute for fixed-source lighting.
SIGNS
Because of the relatively high speeds expected on the proposed roads some variation from the standards recommended by the Manual on Uniform Traffic Control Devices of the Joint Committee of the American Association of State Highway Officials and the Conference on Street and Highway Safety would be required in the design,
