EFFECT OF SHOULDERS ON SPEED AND LATERAL PLACEMENT OF MOTOR VEHICLES

IN ORDER FOR SHOULDERS TO BE EFFECTIVE AND SAFE, THEY MUST BE OF A DESIGN WHICH WILL ENCOURAGE VEHICLES TO TRAVEL CLOSE TO THE PAVEMENT EDGE, THEREBY ALLOWING THE MAXIMUM LATERAL CLEARANCE BETWEEN VEHICLES MEETING ONE ANOTHER. WHEN TWO- LANE PAVEMENTS ARE 20 FT. IN WIDTH OR LESS, SHOULDERS SHOULD BE CONSTRUCTED WITH AT LEAST 4 FT. OF STABILIZED MATERIAL ADJACENT TO THE PAVEMENT, PLUS ADDITIONAL WIDTH OF GRASS OR GRAVEL. THE SPEED OF MOVING VEHICLES IS NOT SUBSTANTIALLY AFFECTED BY THE WIDTH OF SHOULDER, PROVIDING THE SHOULDER IS MORE THAN 4 FT. IN WIDTH. THE LATERAL POSITION OF FREE- MOVING VEHICLES AND THE CLEARANCE BETWEEN MEETING VEHICLES BEARS NO SIGNIFICANT RELATION TO THE SHOULDER WIDTH ABOVE 4 FT. WELL-MAINTAINED GRASS SHOULDERS HAVE THE SAME EFFECT ON THE SPEED AND LATERAL POSITION OF MOVING VEHICLES AS WELL- MAINTAINED GRAVEL SHOULDERS. /AUTHOR/