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California Temporary Traffic Control Handbook <br />Table A - Recommended Advance Warninq Siqn Spacinq <br />Posted Speed <br />Distance Between Sic <br />ns ** <br />at least L <br />A <br />B <br />C <br />Urban <br />100 <br />100 <br />100 <br />25 mph or less*** <br />Urban <br />250 <br />250 <br />250 <br />more than 25 mph to 40 mph*** <br />Urban more than 40 mph*** <br />350 <br />350 <br />350 <br />Rural <br />500 <br />500 <br />500 <br />Expressway/Freeway <br />1,000 <br />1,500 <br />2,640 <br />Distances are shown in feet. The column headings A, B, and C are the dimensions <br />shown on drawings No. 1-48. The A dimension is the distance from the transition or <br />point of restriction to the first sign. The B dimension is the distance between the first <br />and second signs. The C dimension is the distance between the second and third <br />signs. (The "first sign" is the sign in a three -sign series that is closest to the TTC zone. <br />The third sign is one in a three sign series encountered by a driver/motorist <br />approaching a TTC zone). <br />*** Posted speed limit, off-peak 85' percentile speed prior to work starting, or the <br />anticipated operating speed in mph. <br />Table B - Taper Length Criteria for Temp rary Traffic Control Zones <br />Type of Taper <br />Taper Length L <br />Merging Taper <br />at least L <br />Shifting Taper <br />at least 0.5L <br />Shoulder Taper <br />at least 0.33L <br />One -Lane, Two -Way Traffic Taper <br />50 feet minimum, 100 feet maximum <br />Downstream taper <br />50 feet min., 100 feet max. per lane <br />Table C - Formulas for Determining Tape Lengths <br />Speed Limit Taper Length L Feet <br />40 mph or less L = WS2/60 <br />45 mph or more L = WS <br />Where: L = taper length in feet <br />W = width of offset feet <br />S = posted speed limit, or off peak 85th- percentile speed prior to work <br />starting. Or the anticipated operating speed in mph <br />fF <br />