Explanation Given: The speed limit is 55 mi / h . The peak hour factor is 0.80 . The peak hour volume is 1900 . Formula Used: Write the expression for the analysis flow rate. v p = V P H F × N × f HV …… (I) Here, v p is the flow rate, V is the hourly volume, P H F is the peak hour factor, N is the number of lanes and f HV is the heavy vehicle adjustment factor. Write the expression for the heavy vehicle adjustment factor. f HV = 1 1 + P T ( E T − 1 ) …… (II) Here, P T is the proportion of the heavy vehicles and E T is the passenger car equivalent for heavy vehicles. Write the expression for capacity at peak hour. c = Min [ 1900 + 20 ( F F S − 45 ) , 2300 ] …… (III) Here, c is the capacity and F F S is the free flow speed. Write the expression for average speed. S = F F S − ( F F S − c 45 ) ( v P − 1400 ) 1.31 ( c − 1400 ) 1.31 …… (IV) Write the expression for density of traffic stream. D = v p S …… (V) Here, D is density and S is the average passenger car speed. Write the expression for percentage of heavy vehicles. P T = heavy vehicles total vehicles …… (VI) Here, P T is the percentage of heavy vehicles. Calculation: Substitute 1900 veh / h for V , 2 for N , 1 for f HV and 0.80 for P H F in equation (I). v P = 1900 veh / h 0.80 × 2 × 1 = 1900 1.6 = 1187.5 pc / h / ln The v P is less than 1400 pc / h / ln so, S will be equal to F F S . Substitute 1187.5 pc / h / ln for v P and 55 mi / h for S in equation (V). D = 1187.5 pc / h / ln 55 mi / h = 21.59 pc / mi / ln Substitute 150 for heavy vehicles and 1900 for total vehicles in equation (VI). P T = 150 1900 = 0.078 ≈ 0.08 Refer Table 6.10 “LOS criteria for basic freeway segments “Principles of Highway Engineering and traffic, 6 th Edition”. The density 21.59 pc / mi / ln lies in the category LOS C before development. Refer Table 6.7 “Passenger car equivalent for extended freeway segments” of the book “Principles of Highway Engineering and traffic, 6 th Edition. The passenger car equivalent for 5.5 % upgrade, 0.625 mi length and 8 % heavy vehicles is 4.05 . The passenger car equivalent for 4.5 % upgrade, 0

The new level of service of the highway.

Principles of Highway Engineering and Traffic Analysi (NEW!!)

6th Edition

ISBN: 9781119305026

Author: Fred L. Mannering, Scott S. Washburn

Publisher: WILEY

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