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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.
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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)
