This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Highway Capacity Manual 2000 Chapter 23 - Basic Freeway Segments 23-18 Example Problems EXAMPLE PROBLEM 1 The Freeway Existing four-lane freeway, rural area, very restricted geometry, rolling terrain, 70-mi/h speed limit. The Question What is the LOS during the peak hour? The Facts √ Two lanes in each direction, √ 5 percent trucks, √ 11-ft lane width, √ 0.92 PHF, √ 2-ft lateral clearance, √ 1 interchange per √ Commuter traffic, mile, and √ 2,000-veh/h peak-hour volume √ Rolling terrain. (one direction), Comments √ Assume 0 percent buses and RVs since none are indicated. √ Assume BFFS of 75 mi/h for rural areas. √ Assume that the number of lanes does not affect free-flow speed, since the freeway is in a rural area. √ Assume f p = 1.00 for commuter traffic. Outline of Solution All input parameters are known. Demand is computed in terms of passenger cars per hour per lane, an FFS is estimated, and the LOS is determined from the speed-flow graph. An estimate of passenger-car speed is determined from the graph, and a value of density is calculated using speed and flow rate. The calculation of speed is based on the equation found in Exhibit 23-3. Steps 1. Convert volume (veh/h) to flow rate (pc/h/ln) ( use Equation 23-2 ). v p = V (PHF)(N)(f HV )(f p ) v p = 2,000 (0.92)(2)(f HV )(1.00) 2. Find f HV ( use Exhibit 23-8 and Equation 23-3). f HV = 1 1 + P T (E T – 1) + P R (E R – 1) f HV = 1 1 + 0.05(2.5 – 1) + 0 f HV = 0.930 3. Find v p ( use Equation 23-2 ). v p = 2,000 (0.92)(2)(0.930)(1.00) = 1,169 pc/h/ln 4. Compute free-flow speed ( use Exhibits 23-4, 23-5, 23-6, 23-7, and Equation 23-1 ). FFS = BFFS – f LW – f LC – f N – f ID FFS = 75 – 1.9 – 2.4 – 0.0 – 2.5 FFS = 68.2 mi/h 5. Determine level of service ( use Exhibit 23-2 ). LOS B The Results LOS = B, Speed = 68 mi/h, and Density = 17 pc/mi/ln. Highway Capacity Manual 2000 23-19 Chapter 23 - Basic Freeway Segments Example Problems Example Problem 1 1 1 + P T (E T – 1) + P R (E R – 1) V or DDHV PHF * N * f HV * f p V or DDHV PHF * N * f HV * f p V or DDHV PHF * N * f HV * f p Analyst ________________________ Highway/Direction of Travel _____________________ Agency or Company ________________________ From/To _____________________ Date Performed ________________________ Jurisdiction _____________________ Analysis Time Period ________________________ Analysis Year _____________________ q q q q q q Operational (LOS) Design (N) Design (v p ) Planning (LOS) Planning (N) Planning (v p ) Volume, V ___________________veh/h Peak-hour factor, PHF _______________ Annual avg. daily traffic, AADT ___________________veh/day % Trucks and buses, P T _______________ Peak-hour proportion of AADT, K ___________________ % RVs, P R _______________ Peak-hour direction proportion, D ___________________ General terrain DDHV = AADT * K * D ___________________veh/h q Level q Rolling q Mountainous Driver type q Commuter/Weekday q Recreational/Weekend Grade Length _________ mi...
View Full Document
This note was uploaded on 07/13/2011 for the course CME 302 taught by Professor Lin during the Fall '08 term at Ill. Chicago.
- Fall '08