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OCR for page 79
79 Transit LOS Score = 6.0 - 1.50 * TransitWaitRideScore Exhibit 87. Headway Factor Values. + 0.15 * PedLOS (Eq. 23) Headway (min) Frequency (bus/h) fh Where 60 1 1.00 45 1.33 1.33 PedLOS = The pedestrian LOS numerical 40 1.5 1.50 value for the facility (A=1, F=6). 30 2 2.00 TransitWaitRideScore = The transit ride and waiting time 20 3 2.44 score, a function of the average 15 4 2.80 12 5 2.99 headway between buses and the 10 6 3.16 perceived travel time via bus. 7.5 8 3.37 6 10 3.58 The computed transit LOS score is converted to a letter 5 12 3.79 LOS grade using the equivalencies given in Exhibit 86. These NOTE: The following frequency elasticities are assumed: are the same thresholds as used for auto. +1.0 for 1-2 buses/hour, +0.5 for 2-4 buses/hour, +0.3 for 4-6 buses/hour, and +0.2 for 6 or more buses/hour. Elasticities derived from data reported in TCRP Report 95, Estimation of the Pedestrian LOS Chapter 9. The pedestrian LOS for the urban street is estimated using Where the pedestrian LOS model described in a later chapter. F(PTTR) = Perceived Travel Time Factor PTTR = Perceived Travel Time Rate (min/mi) Estimation of the Transit Wait Ride Score BTTR = Base Travel Time Rate (min/mi). Use 6 minutes per mile for the main central business district of The transit wait and ride score is a function of the headway metropolitan areas with population greater than between buses and the perceived travel time via bus for the or equal to 5 million. Use 4 minutes per mile for urban street. all other areas. TransitWaitRideScore = fh * fptt (Eq. 24) e = ridership elasticity with respect to changes in the travel time rate. The suggested default value is Where -0.40, but local values may be substituted. fh = headway factor = the multiplicative change in ridership expected on a route at a headway h, relative to the rider- Exhibit 88 below illustrates the application of this equation ship at 60-minute headways; for selected perceived travel time rates and a selected elasticity. fptt = perceived travel time factor = the multiplicative change The perceived travel time rate (PTTR) is estimated based in ridership expected at a perceived travel time rate on the mean speed of the bus service, the average excess wait PTTR, relative to the ridership expected at a baseline time for the bus (due to late arrivals), the average trip length, travel time rate. the average load factor for the bus service, and the amenities The baseline travel time rate is 4 minutes/mile except at the bus stops. for central business districts of metropolitan areas with Exhibit 88. Example Perceived over 5 million population, in which case it is 6 min/mile. Travel Time Factors (F(PTTR)). Exhibit 87 provides fh values for typical bus headways. F(PTTR) The perceived travel time factor is estimated based on the BTTR: 4 min/mi 6 min/mi perceived travel time rate and the expected demand elasticity PTTR for a change in the perceived travel time rate. (min/mi) 2 1.31 1.50 FPTTR = [(e - 1) BTTR - (e + 1)TTR ] (Eq. 25) 2.4 1.22 1.41 [(e - 1)TTR - (e + 1) BTTR ] 3 4 1.12 1.00 1.31 1.17 6 0.85 1.00 12 0.67 0.76 Exhibit 86. Transit LOS Thresholds. 30 0.53 0.58 Notes: LOS Numerical Score F(PTTR) = Perceived Travel Time Factor A 2.00 PTTR = Perceived Travel Time Rate. B >2.00 and 2.75 BTTR = Base Travel Time Rate (default is 4 minutes per mile. 6 minutes per mile BTTR C >2.75 and 3.50 is used for the central business districts D >3.50 and 4.25 (CBDs) of metropolitan areas with 5 million E >4.25 and 5.00 or greater population). F > 5.00 Based on default value of 0.40 for elasticity.

OCR for page 79
80 PTTR= a1 * IVTTR + a2 * EWTR - ATR (Eq. 26) Exhibit 89. Passenger Load Weighting Factor (a1). Where PTTR = perceived travel time rate. Load Factor IVTTR = actual in-vehicle travel time rate, in minutes per (pass/seat) a1 0.80 1.00 default mile. 1.00 1.19 EWTR = excess wait time rate due to late arrivals = excess 1.10 1.41 wait time (minutes) / average trip length (miles). 1.20 1.62 a1 = passenger load weighting factor (a function of the 1.30 1.81 average load on buses in the analysis segment dur- 1.40 1.99 1.50 2.16 ing the peak 15 minutes). 1.60 2.32 a2 = 2 = wait time factor, converting actual wait times Notes: into perceived wait times. Load factor is the average ratio of ATR = amenity time rate = perceived travel time rate re- passengers to seats for buses at the peak load point within the study duction due to the provision of certain bus stop section of the street.If bus load amenities = in-vehicle travel time value of stop factor is not known, a default value of 1.00 can be assumed for the amenities (minutes) / average trip length (miles). load weighting factor (a1). In-Vehicle Travel Time Rate The excess wait time rate is the excess wait time (in min- The in-vehicle travel time rate is equal to the inverse of the utes) divided by the mean passenger trip length for the bus mean bus speed converted to minutes per mile. route(s) within the study section of the street. 60 For average passenger trip length, a default value can be IVTTR = (Eq. 27) Speed taken from national average data reported by the American Public Transit Association (APTA) http://www.apta.com/ Where research/stats/ridership/trlength.cfm ). In 2004, the mean IVTTR = In-Vehicle Travel Time Rate (min/mi)r. trip length for bus passenger-trips nationwide was 3.7 miles. Speed = Average speed of bus over study section of street More locally specific values of average trip length can be (mph). obtained from the NTD. Look up the annual passenger miles When field measurement of mean bus speed is not feasible, and annual unlinked trips in the transit agency profiles stored the mean schedule speed can be used. Identify two schedule under NTD Annual Data Publications at http://www.ntd points on the published schedule for the bus route(s). Mea- program.gov/ntdprogram/pubs.htm#profiles. The mean trip sure the distance covered by the bus route(s) between the two length is the annual passenger-miles divided by the annual points. Divide the measured distance by the scheduled travel unlinked trips. time between the two schedule points. The bus speed estima- tion procedure given in Chapter 27 (Transit) may be used to Amenity Time Rate estimate future bus speeds. The in-vehicle travel time rate is multiplied by a passenger The amenity time rate is the time value of various bus stop load weighting factor (a1) to account for the increased dis- improvements divided by the mean passenger trip length. comfort when buses are crowded. Values of the passenger The mean passenger trip length is the same distance used to load weighting factor (a1) are given in Exhibit 89. compute the Excess Wait Time Rate (described above). 1.3 * Shelter + 0.2 * Bench ATR = (Eq. 28) Excess Wait Time Rate ATL The excess wait time is the sum of the differences between Where the scheduled and actual arrival times for buses within the ATR = Amenity Time Rate (min/mi) study section of the street divided by the number of observa- Shelter = Proportion of bus stops in study section direction tions. Early arrival without a corresponding early departure is with shelters counted as being on-time. However, early arrival with an early Bench = Proportion of bus stops in study section direction departure is counted as being "one headway" late for the pur- with benches poses of computing the average excess wait time for the street. ATL = Average passenger trip length (miles)