HIGHWAY CAPACITY & LEVEL OF SERVICE (LOS) THE USED OF ROAD CAPACITY AND LOS ARE… Seek to measure Highway Performance (Congestion). Needed for: Highway construction Congestion relief

WHAT IS ROAD CAPACITY ? Road capacity is the maximum potential capacity of a given roadway (can be expressed in terms of vehicles per hour or per day) or… 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

WHAT IS LEVEL OF SERVICE (LOS) ? The level of service provides a qualitative ranking of the traffic operational conditions experienced by users of a facility

FREEWAYS/MULTILANE HIGHWAY CAPACITY STUDY Highway Capacity Manual defines the LOS categories for freeways and multilane highways as follows: 6 levels of service: LOS A Very Good LOS B LOS C LOS D LOS E LOS F Very Poor

LOS A Free-flow conditions users are virtually unaffected by the presence of others in the traffic stream. Freedom to select desired speeds Excellent in level of comfort and convenience LOS B Allows speeds at or near free-flow speeds, The presence of other users in the traffic stream begins to be noticeable. Freedom to select desired speeds is relatively unaffected, A slight decline in the freedom to maneuver within the traffic stream relative to LOS A. LOS C Speed at or near free-flow speeds, Freedom to maneuver is noticeably restricted (lane changes require careful attention on the part of drivers). Level of comfort and convenience declines significantly (Disruptions in the traffic stream) Result in significant queue formation and vehicular delay. LOS D Speeds begin to decline slightly with increasing flow. The freedom to maneuver becomes more restricted and drivers experience reductions in physical and psychological comfort. Generate lengthy queues LOS E LOS E represents operating conditions at or near the roadway’s capacity. maneuverability is extremely limited and drivers experience considerable physical and psychological discomfort. LOS F describes a breakdown in vehicular flow. Vehicles typically operate at low speeds in these conditions and are often required to come to a complete stop.

LEVEL OF SERVICE DETERMINATION Base Conditions Lane widths, Lateral clearances, Access frequency (non access controlled highways), Terrain; Traffic stream conditions such as the effects of heavy vehicles (large trucks, buses and RVs), and driver population characteristics.

MULTILANE HIGHWAY CAPACITY STUDY A MULTILANE HIGHWAY ...... Has a posted speed limit of 60 to 90 km/h. Has a total of 4 to 6 lanes. Often is divided (has a median), can also be undivided. Is situated in suburban communities, leading into cities. Is also situated along high-volume rural corridors connecting two cities. Has traffic signals spaced at 3 km or less. Accommodates 15,000 – 40,000 vehicles per day. May accommodate as high as 100,000 veh/day when access across the median is restricted and when all major crossings are grade separated.

MULTILANE HIGHWAY CAPACITY STUDY Divided highway Undivided highway TWLT Lane median At-grade crossing Grade separated crossing

MULTILANE HIGHWAY CAPACITY STUDY Under BASE CONDITIONS, full speed and capacity can be achieved. The base conditions for a multilane highway are ...... 3.6 m minimum lane width. 3.6 m minimum total lateral clearance in the direction of travel. Only passenger cars in the traffic stream. No direct access points along the roadway. Highway is divided. Free flow speed (FFS) is greater than 100 km/h.

MULTILANE HIGHWAY CAPACITY STUDY Total Lateral Clearance = Median Lateral + Shoulder Lateral Clearance Clearance 1.6 m 1.2 m Median Roadway Shoulder Total Lateral Clearance = 1.6 + 1.2 = 2.8 m * If lateral clearance (shoulder or median) is greater than 1.8 m, the lateral clearance is taken as 1.8 m.

MULTILANE HIGHWAY CAPACITY STUDY Calculate the total lateral clearance. 2.4 m 1.2 m Total Lateral Clearance =

@ W MULTILANE HIGHWAY CAPACITY STUDY Calculate the total lateral clearance. @ 0.8 m 1.25 m W 2.5 m 1.7 m Total Lateral Clearance =

MULTILANE HIGHWAY CAPACITY STUDY ACCESS POINTS on a highway includes Driveways and Intersections

MULTILANE HIGHWAY CAPACITY STUDY Methodology (accroding to HCM 2000) FFS BFFS BFFS Adjustment Lane width Median type Access point Lateral Clearance Compute FFS Input Geometric data FFS or BFFS volume Determine LOS Volume Adjustment Peak-hour Factor Number of Lanes Driver population Heavy vehicles Compute flow rate

MULTILANE HIGHWAY CAPACITY STUDY DETERMINATION OF FREE FLOW SPEED (FFS) (a) Field Measurement Average of all passenger car speeds measured in field under low volume conditions. If the flow rate during field observation is at or below 1400 pc/hr/Lane, it can be use directly as FFS (b) Estimation FFS = BFFS – fW – fLC – fM – fA where BFFS = base free flow speed fw = adjustment for lane width fLC = adjustment for lateral clearance fM = adjustment for median fA = adjustment for access point density

MULTILANE HIGHWAY CAPACITY STUDY (b) Estimation BFFS is assumed to be 3 km/h lower than the 85th percentile speed. Recent studies suggests that BFFS is approximately 11 km/h higher than the speed limits of 65 km/h and 70 km/h, and it is 8 km/h higher for 80 km/h and 90 km/h speed limits. The BFFS is then reduced by the adjustment factors for lane width, lateral clearance, median type and access point density. The adjustment factors can be determined from the tables in HCM2000.

MULTILANE HIGHWAY CAPACITY STUDY DETERMINATION OF FLOW RATE (vP) vP = V PHF x N x fHV x fp where V = hourly volume (veh/hr) PHF = peak hour factor N = number of lanes (per direction) fHV = heavy vehicles adjustment factor fp = driver population factor Peak Hour Factor PHF = V where V = peak hourly volume 4 x V15 V15 = highest 15-minute volume

MULTILANE HIGHWAY CAPACITY STUDY When PHF data is not available, assume 0.88 for rural multilane highways and 0.92 suburban multilane highways. Quick Exercise Calculate the peak hour factor from the following traffic count: Time Traffic count 8:00 – 8:15 102 8:15 – 8:30 98 8:30 – 8:45 116 8:45 – 9:00 104 PHF = 102 + 98 + 116 + 104 4 x 116 = 0.90

MULTILANE HIGHWAY CAPACITY STUDY Heavy Vehicle Adjustment Factor fHV = 1 1 + PT (ET – 1) + PR (ER – 1) where PT = percentage of trucks and buses ET = passenger car equivalent for trucks and buses PR = percentage of recreational vehicles ER = passenger car equivalent for recreational vehicles * Neglect PR and ER , because there are no RVs in Malaysia! Recreational vehicle (RV)

MULTILANE HIGHWAY CAPACITY STUDY Driver Population Factor When the traffic stream is made up of vehicles driven by regular drivers (commuters, or drivers familiar with the highway), the driver population factor, fP is taken as 1.00 Driver population factor may range between 0.85 and 1.00 DETERMINATION OF LEVEL OF SERVICE LOS is determined using the FFS and vP values. Look up the Speed-Flow curve. Locate the vP value on the x-axis and draw a vertical line upwards. Determine the average speed, S. (S=FFS if vP ≤ 1400 pc/hr/ln) Calculate density, D = vP / S. Determine the LOS on basis of density region in which the point is located.

MULTILANE HIGHWAY CAPACITY STUDY Quick Excercise (1) Determine the LOS of a multilane highway, given that FFS is 82.5 km/h and vP = 926 pc/hr/ln. D = vp/S = 926 / 82.5 = 11.2 pc/km/ln LOS C

MULTILANE HIGHWAY CAPACITY STUDY Quick Excercise (2) Determine the LOS of a multilane highway, given that FFS is 78 km/h and vP = 1,540 pc/hr/ln.

WHAT IS FREEWAYS? Divided highway with full access control Has two or more lanes each direction Uninterrupted flow (signalised / stop controlled are not permitted) Basic freeways sections : outside influence area of ramps or weaving areas Merging/diverging occurs where on or off-ramps join the basic freeway section.

Base free-flow Characteristics Lane : 3.6 m wide Lateral clearance between edge of a right lane obstacle is 1.8m or greater No trucks, buses or RVs in traffic stream Urban freeways = 5 lanes in each direction. Interchanges are spaced at least 3.2 km apart Grades do not exceed 2% Drivers are familiar with the freeways

LOS FOR FREEWAY SEGMENTS Basically has similar step with multilane But it use different figure / table. ha

Or turn to page 407 from text book in mph unit