Explanation Given: The lane width is 11 ft . The right shoulder width is 4 ft . The speed limit is 55 mi / h . The peak hour factor is 0.80 . Formula Used: Write the expression for estimated free flow speed. B F F S = speed limit + 5 mi / h …… (I) Here, B F F S is the estimated free flow speed. Write the expression for the free flow speed. F F S = B F F S − f LW − f TLC − f M − f A …… (II) Here, F F S is the free flow speed, B F F S is the free flow sped for base condition, f LW is the adjustment for lane width, f TLC is the adjustment for total lateral clearance, f M if the adjustment for median type and f A is the adjustment for number of access points. Write the expression for the analysis flow rate. v p = V P H F × N × f HV …… (III) 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 ) …… (IV) 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 ] …… (V) Here, c is the capacity and F F S is the free flow speed. Calculation: Substitute 55 mi / h for speed limit in equation (I). B F F S = 55 mi / h + 5 mi / h = 60 mi / h Refer Table 6.3 “Adjustment of the lane width” of the book “Principles of Highway Engineering and traffic, 6 th Edition. The f LW for lane width 11 ft is 1.9 mi / h . Refer Table 6.11 “Adjustment of lateral clearance” of the book “Principles of Highway Engineering and traffic, 6 th Edition.” The f TLC for shoulder on right side 6 ft + 4 ft is 0.4 mi / h . Refer Table 6.12 “Adjustment of median type” of the book “Principles of Highway Engineering and traffic, 6 th Edition.” The f M for un-median type is 1.6 mi / h . Refer Table 6

The directional hourly volume.

PRINCIPLES OF HIGHWAY ENGINEERING+TRAFF

7th Edition

ISBN: 9781119688372

Author: Mannering

Publisher: WILEY

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