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California Temporary Traffic Control Handbook <br />18 <br />Table A - Recommended Advance Warning Sign Spacing <br />Posted Speed Distance Between Signs ** <br />A B C <br />Urban <br />25 mph or less***100 100 100 <br />Urban <br />more than 25 mph to 40 mph***250 250 250 <br />Urban more than 40 mph***350 350 350 <br />Rural 500 500 500 <br />Expressway/Freeway 1,000 1,500 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 85th percentile speed prior to work starting, or the <br />anticipated operating speed in mph. <br />Table B - Taper Length Criteria for Temporary Traffic Control Zones <br />Type of Taper Taper Length (L) <br />Merging Taper at least L <br />Shifting Taper at least 0.5L <br />Shoulder Taper at least 0.33L <br />One-Lane, Two-Way Traffic Taper 50 feet minimum, 100 feet maximum <br />Downstream taper 50 feet min., 100 feet max. per lane <br />Table C - Formulas for Determining Taper 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