PHILADELPHIA UNIVERSITY Faculty of Engineering. Department of Civil Engineering.

1. PHILADELPHIA UNIVERSITY Faculty of Engineering. Department of Civil Engineering. Transportation and Traffic Engineering Ch 2 Capacity & LOS Concepts Reference: HCM 2000 Ch2 1

2. Highway Capacity & Level of Service HCM2000 2

3. Capacity The capacity of a facilityis the maximum hourly rate at which persons or vehicles reasonably can be expected to traverse a point or a uniform section of a lane or roadway during a given time period under prevailing roadway, traffic, and control conditions Capacity analysis tries to give a clear understanding of how much traffic a given transportation facility can accommodate. 3

4. Prevailing roadway, traffic, and controlconditions define capacity; these conditions should be reasonably uniform for any section of facility analyzed - Any change in the prevailing conditionschanges the capacity of the facility

5. Factors affecting highway capacity Geometric conditions: like: •Lane width. •Width of shoulders. •Lateral clearance. •Road alignment (horizontal and vertical) and geometry. Traffic conditions: like: •On way or two way traffic and number of lanes. •Driver and vehicular characteristics. •Single type or mixed traffic. Weather conditions. •Parking characteristics. •Presence of pedestrians. •Presence of public transportation stops. 5

6. Ideal roadway conditions Ideal roadway conditions assume good weather, good pavement conditions, users familiar, and: • Uninterrupted flow • Passenger cars only in the traffic stream • Traffic lane 12 ft (3.6 m) wide. • adequate shoulders and no lateral obstructions within 6 ft (1.8 m) of the edge of the pavement . • Free-flow speed of 100 km/h for multilane highways, • Level terrain, • No obstructions to through traffic due to traffic control or turning vehicles. • No-passing zones on two-lane highways. 6

7. Ideal Capacity Such a facility is considered as an ideal facility The following values can be taken as capacity (HCM 2000): -Freeways: 2,400 pcphpl -Multilane highway: 2,200 pcphpl 7

8. Level of service (LOS) 8

9. Level of service (LOS) • The LOS depending upon the travel speed and v/c ratio. • The ratio v/c can vary between 0 and 1. • Levels represent range of operating conditions defined by measures of effectiveness (MOE). • Letters designate each level, from A to F. • LOS A representing the best operating conditions • LOS F representing the worst operating conditions. 9

10. Factors affecting Level of Service LOS is a quality measure describing operationalconditions within a traffic stream. • Travel speed • Traffic interruptions • Freedom to maneuver and maintain operating speed • Safety • Driving comfort • Vehicular operating cost over particular section 10

11. The service flow rate is the maximum hourly rate at which persons or vehicles can be expected to traverse a point or uniform segment of a lane or roadway during a given period under prevailing roadway, traffic, and control conditions while maintaining a designated level of service 11

12. Level of Service (LOS) LOS A: -Free-flow operation, with speeds controlled bydriver desirers, speed limit, and physical roadway conditions - Maneuverability is good 12

13. LOS B: - Speeds begins to be restricted -Reasonably free flow, -Ability to maneuver is only slightly restricted,

14. LOS C: Speeds and maneuverability are more closely controlled by the higher volume -Freedom to maneuvers is noticeably restricted, 14

15. LOS D: -Approaches unstable flow, speeds aremore controlled by operating conditions (compared to LOS C)

16. LOS E: -Speeds lower than those forLOS D and volumes at or close to capacity of the highway 16

17. LOS F: -Describes forced flow operation at low speeds, wherevolumes are below capacity.

18. Design Level of Service This is the desired quality of traffic conditions from a driver’s perspective (used to determine number of lanes) - Design LOS is higher for higher functional classes - Design LOS is higher for rural areas - LOS is higher for level/rolling than mountainous terrain - Design all elements to same LOS (use HCM to analyze)

19. Design Level of Service (LOS)

20. Transportation and Traffic Engineering Traffic Volume

21. Variation of Traffic Volume Several types of measurements of volume are commonly adopted which will be used in many design purposes: 1- Average Annual Daily Traffic (AADT): The average 24-hour traffic volume at a given location over a full 365-day year, i.e. the total number of vehicles passing the site in a year divided by 365. 2- Average Daily Traffic (ADT): An average 24-hour traffic volume at a given location for some period of time less than a Year. It may be measured for six months, a season, a month, a week, or as little as two days.

22. Traffic forecasting 22 Traffic forecasting is the process of estimating the number of vehicles or people that will use a specific transportation facility in the future. Future AADT = Current AADT x (1 + AAGR) n Where : n = number of years. AAGR = Average Annual Growth Rate used to develop the future traffic forecast.

23. Traffic forecasting 23 Example: If AADT for the year 2016 = 2500 pcu/day. Find the AADT for the year 2036, if the AAGR = 3%. Solution: 2033 AADT = 2016 AADT x (1 + AAGR)n. = 2500 x ((1+0.03) ^20 ). = 2500 x 1.806 = 4515 pcu/day.

24. Design Hourly volume •In design, peak-hour volumes are sometimes estimated from projections of the AADT (Both directions). •Design hourly volume (DHV): - Traffic volume used for design calculations • Typically between 10th and 50th highest volume hour of the year.

25. Which hour? -Usually use 30 highest hourly volume of the year. Why 30 DHV? Compromise: too high is wasteful too low poor operation Design Hourly Volume (DHV): - Future hourly volume (both directions) used for design, typically 30 DHV in the design year

27. Design Hourly volume DHV = K * AADT K: is defined as the proportion of annual average daily traffic occurring in an hour For urban, suburban: K= 8%-12% D = For rural: K= D=

28. Design Hourly volume •Directional Design Hourly Volume (DDHV): Directional distribution factor (D): - Factor reflecting the proportion of peak-hour traffic traveling in the peak direction. - Often there is much more traffic in on direction than the other.

29. Example Urban freeway, 2 lanes each direction. ,Passenger car only facility, AADT = 35000 v/day, Directional split = 65/35 %. Find the Directional Design Hourly Volume DDHV. Solution: From the table: K= 0.10 (from table for urban freeway). Directional Design Hourly Volume (DDHV): DDHV = AADT*K*D = 35000 *0.10*0.65 = v/h.

30. Rates of flow Generally stated in units of "vehicles per hour," but represent flows that exist for periods of time less than one hour. •A volume of 200 vehicles observed over a 15-minute period may be expressed as a rate of 200 * 4 = 800 v/h. 800 v/h becomes a rate of flow that exists a 15-minute interval.

31. Volume & Flow rate The distinction between volume and flow rate is important. Volume is the number of vehicles observed or predicted to pass a point during a time interval. Flow rate represents the number of vehicles passing a point during a time interval less than 1 h, but expressed as an equivalent hourly rate.

32. Example/ Find the volume and the flow rate? Solution: The total hourly volume = 4,300 v/h. The flow rate, however, varies for each 15-min period. During the I5-min period of maximum flow, the flow rate = 1,200 v/0.25h, or 4,800 v/h.

33. Peak-hour factor Peak flow rates and hourly volumes produce the peak-hour factor (PHF), the ratio of total hourly volume to the peak flow rate within the hour, computed by Equation: * If 15-min periods are used, the PHF may be computed by Equation Where: PHF = peak- hour factor V = hourly volume (v/h) and V15 = volume during the peak 15 min of the peak hour(v/15 min).

34. Example: Give 15 minute flow of 1000, 900, 800, 850 v/15 What is the peak hour factor. Solution: V15 = 1000 v/15. V= ( 1000+900+800+850)= 3550 v/h. PHF= 3550/(4*1000)=0.89. PHF generally range from 0.85 to 1.00.

35. Number of lane