Morrisville Engineering, Design, and Construction Manual - July 2016

Section 4: Access and Circulation 4.2 Streets and Alleys 4.2.6 Intersection Sight Distance Areas

Intersection Sight Distance

1. Intersection sight distance is based on conflicts with opposing vehicles rather than with objects located in the roadway. 2. At all vehicular accessway intersections, there is a minor street, driveway, or movement (whose approach may be controlled by some device such as a sign), and a major street or movement (whose approach may not be controlled).The amount of sight distance required at an intersection depends on the type of traffic control device (e.g. stop sign) at the intersection and the speed of the vehicle approaching the intersection. 3. Intersection sight distance is measured in the horizontal (plan) and vertical (profile) planes. In both situations, a driver must be offered an unobstructed line of sight to the roadway they wish to cross or join. The horizontal intersection sight distance is measured along the centerline of the major street between the drivers of the two opposing vehicles. 4. Some conditions may exist that prevent the attainment of desirable sight distance. In such cases, the sight distance shall be obtained to the maximum practicable and additional measures such as warning signs, reduced speed zones, and other traffic controls may be required by the Town Engineer. 5. A minimum 10 foot by 70 foot sight triangle easement shall be dedicated on the recorded plat to restrict the uses in this area from obstructing the line of sight from the intersection. No permanent object greater than 3.5 feet in height shall be constructed in this area. If the Sight distance as measured by the AASHTO or NCDOT method falls outside of the 10’x70’ area, the dedicated area shall based off of this line.

Relationship to Intersection Traffic Controls

1.

Yield Sign Control

For intersections utilizing a yield sign, the following is required.

a. The intersection sight distance for the driver on the side street (minor movement) must be sufficient for the driver to observe a vehicle on the through street (major movement) approaching from either the left or the right and bring his/her vehicle to a stop prior to reaching the intersection.

b. Adequate sight distance shall be provided for safe departure from a stopped condition.

2.

Stop Sign Control

For intersections utilizing a stop sign, the following is required.

a. The driver of the stopped vehicle shall have adequate sight intersection distance to cross or join the approaching traffic flow without adversely affecting the travel speed of the approaching traffic.

b. There are three basic maneuvers that occur at stop controlled intersections:

(1) To travel across the intersecting roadway by clearing traffic on both the left and the right of the crossing vehicle; (2) To turn left into the crossing roadway by first clearing the traffic on the left and then entering the traffic stream with vehicles from the right (this maneuver is similar in nature to that made by the median left turns off the through street); and (3) To turn right into the intersecting roadway by entering the traffic stream with vehicles from the left. c. Where the through street is undivided or divided with a median narrower than 20 feet, maneuvers b(1) and b(2) are treated as a single operation. d. Where the median can provide storage for the design vehicle (20 feet wide for a passenger car), maneuvers b(1) and b(2) may be considered in two separate phases of operation.

January 2016

Morrisville, NC

Page 16

Engineering, Design, and Construction Manual