Explanation Given: The lane width is 10 ft . The right shoulder width is 6 ft . The left shoulder width is 3 ft . The speed limit is 50 mi / h . The peak hour factor is 0.95 . 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 speed 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 the 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. Write the expression for average speed. S = F F S − ( F F S − c 45 ) ( v P − 1400 ) 1.31 ( c − 1400 ) 1.31 …… (VI) Write the expression for density of traffic stream. D = v p S …… (VII) Here, D is density and S is the average passenger car speed. Calculation: Substitute 50 mi / h for speed limit in equation (I). B F F S = 50 mi / h + 5 mi / h = 55 mi / h Refer Table 6.3 “Adjustment for the lane width” of the book “Principles of Highway Engineering and traffic, 6 th Edition.” The f LW for a lane width of 10 ft is 6.6 mi / h . Refer Table 6.11 “Adjustment for lateral clearance” of the book “Principles of Highway Engineering and traffic, 6 th Edition.” The total lateral clearance is calculated as, T L C = ( Right side shoulder ) + ( Left side shoulder ) = 6 ft + 3 ft = 9 ft The f TLC for a four lane highway having a total lateral clearance of 10 ft is 0.4 mi / h . The f TLC for a four lane highway having a total lateral clearance of 8 ft is 0.9 mi / h . The f TLC for the total lateral clearance of 9 ft using interpolation is, x = ( 0.9 mi / h ) − ( 9 ft − 8 ft ) ( 0.9 mi / h − 0.4 mi / h ) ( 10 ft − 8 ft ) = 0.9 mi / h − 0.25 mi / h = 0.65 mi / h Refer Table 6.12 “Adjustment for median type” of the book “Principles of Highway Engineering and traffic, 6 th Edition.” The f M for divided highwayis 0.0 mi / h . Refer Table 6.13 “Adjustment for access point frequency” of the book “Principles of Highway Engineering and traffic, 6 th Edition.” The reduction in free flow speed for 0 access points per mile is 0.0 mi / h . The reduction in free flow speed for 10 access points per mile is 2.5 mi / h . The f A for 4 access points per mile by interpolation is, x = 2.5 mi / h − ( 10 − 4 ) ( 2.5 mi / h − 0 mi / h ) ( 10 − 0 ) = 2.5 mi / h − 1.5 mi / h = 1.0 mi / h Substitute 1 mi / h for f A , 0.0 mi / h for f M , 0.65 mi / h for f TLC , 6.6 mi / h for f LW and 55 mi/h for B F F S in equation (I). F F S = 55 mi / h − 6.6 mi / h − 0.65 mi / h − 0.0 mi / h − 1 mi / h = 55 mi / h − 8

The new level of service of the highway.

PRINCIPLES OF HIGHWAY ENGINEERING+TRAFF

7th Edition

ISBN: 9781119688372

Author: Mannering

Publisher: WILEY

See similar textbooks

Concept explainers

Intersection Design

An intersection is a location where two or more roads or railways meet or join. The traffic movement is controlled at the intersection that depends on its design and type. It governs the operation, efficiency, speed, capacity, and safety of the highways,…

Question

Chapter 6, Problem 20P

To determine