APPENDIX E: SIGHT DISTANCE REQUIREMENTS

TABLE 7a

SIGHT DISTANCES FOR VEHICLES EXITING FROM ACCESS POINTS ONTO ADJACENT ROADS

D = Distance along major road from access point to allow vehicle to enter safely (feet)

See accompanying illustration (*)

 

Vehicle Type	2 Lane		4 or 6 Lane		2 Lane		4 or 6 Lane		2 Lane		4 or 6 Lane		2 Lane		4 or 6 Lane		2 Lane		4 or 6 Lane
	DL	DR	DL	DR	DL	DR	DL	DR	DL	DR	DL	DR	DL	DR	DL	DR	DL	DR	DL	DR
Passenger car	150	130	130	130	360	260	220	260	530	440	380	440	740	700	620	700	950	1050	950	1,050
Truck	300	200	200	200	500	400	400	400	850	850	850	850	1,600	1,600	1,600	1,600	2,500	2,500	2,500	2,500

 

   TABLE 7b

   LEFT TURN SIGHT DISTANCE FOR VEHICLES ENTERING ACCESS POINTS

S = Sight distance along major route for vehicle to safely turn left into access point (feet)

See accompanying illustration

 

Vehicle Type	20 MPH			30 MPH			40 MPH			50 MPH			60 MPH
	2 Lane	4 Lane	6 Lane	2 Lane	4 Lane	6 Lane	2 Lane	4 Lane	6 Lane	2 Lane	4 Lane	6 Lane	2 Lane	4 Lane	6 Lane
Passenger car	150	160	170	230	250	270	370	390	420	520	550	580	700	740	780
Truck	260	260	300	400	440	480	570	620	670	810	880	950	1,000	1,100	1,200

 

* Measured from a vehicle ten feet back of the pavement edge.

NOTE:

   (A)   Values are for urban conditions. On rural streets, distances are to be increased by 10% to allow for longer drive reaction timing.

   (B)   The sight distances apply when street grades are zero to 3.0% (either up or down). When an upgrade is steeper than 3.0%, adjustments are to be made to compensate for the longer time required to reach the speed of highway traffic. The time is less than shown when the highway is descending. Adjustment factors below apply to grades only in that portion of the road between the access points and the downstream point at which a vehicle is emerging from the access points has been able to accelerate to within ten miles per hour of the route speed.

   (C)   When the street in the section to be used for acceleration after leaving the access point ascends at 3 to 4%, then sight distances in the direction of approaching ascending traffic are to be increased by a factor of 1.4. When the access point ascends at 5 to 6%, sight distance should be increased by a factor of 1.7.

   (D)   When the road in the section to be used for acceleration after leaving the access point descends at 3 to 4%, then sight distance in the direction of approaching descending highway traffic should be reduced by a factor of 0.6. If the road descends at 5 to 6%, sight distance should be reduced by a factor of 0.5.

   (E)   When the criteria for sight distances to the right cannot be met, the need can be eliminated by prohibiting left turns by existing vehicles.

   SIGHT DISTANCE FOR VEHICLES EXITING FROM ACCESS POINTS

   (Refer to Appendix E, Table 7a)

LEFT TURN SIGHT DISTANCE FOR VEHICLES ENTERING ACCESS POINTS

   (Refer to Appendix E, Table 7b)

(1984 Code, Ch. 157, App. E) (Ord. O-85-78, passed 8-17-1978)