|
Abstract The existing method
in "The Highway Capacity Manual(HCM) in Taiwan" forthe
evaluation of capacity and level of service(LOS) on freeway
off-rampjunction is modified from the "Highway Capacity Manual
in U.S.A., 1985". Thepractical applicability is limited, due
to the difference of trafficcharacteristic between Taiwan
and U.S.A.. To improve and enhance theapplicability of the
method, this research, making reference to the 1994revised
edition of HCM in U.S.A., develops an evaluation approach
ofcapacity and LOS on off-ramp junction area, which is more
suitable for thetraffic characteristic in Taiwan. The
contents and approaches of thisresearch are as following:
1. To collect and analyze traffic flow data and characts., such
as volume ,speed,density ect., and develop traffic flow
models. 2. To identify the bottleneck on off-ramp junction
area, which is considered as the main evaluation location.
3. To analyze the number of main lanes influenced by the
behavior of diverging flow on off-ramp junction area. 4.
To develop the volume prediction model for the influenced area
5. To develop the traffic flow models for the influenced lanes,
which are used to evaluate the capacity. 6. To develop
LOS measure of performance models, for the influenced area. 7.
To establish the LOS evaluation procedure and method， that fit
Taiwan''s traffic flow characteristic on off-ramp junction area.
The main conclusions drawn from this study are: 1. The
bottleneck on off-ramp junction area is not fixed. The location
changes mainly with the diverging traffic volume . 2. Lane 1
and Lane 2 of mainline are the influenced area of freeway
off-ramp junction area. This conclusion is same as "HCM in U.S.
A.,1994". 3. This study develops a set of traffic flow models
for the influenced area, using volume~density~speed (K~Q~U)
curve fitting approach, which are used for capacity
evaluation.. For 2 or 3-lane freeway segments, the capacity
is 4,400 pcph (2,200 pcph for each lane). For 4-lane
freeway segments, the capacity is 4,600 pcph(2,300 pcph for each
lane). 4. This study chooses density as the major MOE of LOS.
Speed and V/C volume as secondary MOE. Density and
speed prediction model are developed by use of on-site
data, to be used in LOS evaluation. 5. The critical density is
found to be around 40 pcu/km/ln, which is a different from
the freeway basic segment. Therefore, LOS criteria is
different between off-ramp area and basic segment.
|