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Chapter Four. Field Data Collection
Pages 35-54

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From page 35...
... Data Definition Intersection Geometry Data ·Nllmber of lanes per approach Diane designations ·Grades · Sight distance for non-pnor~ty vehicles Traffic Flow Data ·Traffic flow rates for all movements ·Tr~ic stream composition for all movements ·Proportion of non- platooned vehicles for each priority stream movement · Capacity for each non-prior~ty movement ·Length of peak period Gap "d Headway Data uncritical gap for each non-prior~ty stream ·Follow-up gap for each non-priority stream ·Minimum headway for platooned priority stream Raw Data Required for Model Estimation For Each Vehicle ·Event time at conflict point ·Movement direction ·Vehicle type ·Lane used Additional Data for Each Non-Priority Vehicle ·Event time at back of queue ·Event time et front of queue ·Event time departing queue Computed or Derived Data Required for Model Estimation For Each Traffic Stream ·Flow rates ·Stream composition For Each Non-Priority Stream Vehicle ·Gap event history while et front of queue · Measured or estimated capacity · Service time or delay ·Queue delay aTota1 stopped delay For inch Priority Sbeam Vehicle ·Propofion offree vehicles ·Minimum headway of platooned vehicles . on capacity could be quantified.
From page 36...
... Configuration #3 Geometry Lanes on major sheet = 2 Lanes on minor street = 2 Optional major street exclusive lef`-tuin lane Planned Number of Sites · Urban axe" = 3 · Rural areas = 0 · Total sites = 3 A total of 68 unique sites were videotaped during 79 videotaping time periods. Overall, the sample size objective of 70 TWSC intersections was met.
From page 37...
... TWSC Intersection Videtaping Periods: Geometric Configuration by Major Street Speed 2 Total 4 2 1 7 14 11 7 3' 8 11 6 i, ~ , , _ , ~ , 6 1 Tables 10 and ~ ~ show the breakdown of Me number of sites by geometric configuration and the distance to upstream signal control on the major street. Since the effects of vehicle progression on capacity are significant, it is important to have a mix of sites with varying distances to upstream signal conuo} and Bus varying degrees of progression and/or platooning.
From page 38...
... TWSC Sites Traffic Characteristics SummarY-Sou~west Sector SWTOO1 SWT002 SWT003 SWT004 SWTOOS SWI006 SU'I007 SWTo08 SWT009 SWTO10 SWTO11 SUlT012 SWI013 SWI014 SWT015 SWT016 SWT017 swro~a SWIO19 maximum and average values for 5-minute data points. It is instructive to note the w~de range of flow rates, queue percentage, and delays ~at were exhibited in the field data for each site even dunag one videotape penod of approximately I.5 hours.
From page 39...
... 39 Table 13. TWSC Sites Traffic Characteristics-Southeast Sector B~:1)
From page 40...
... 40 Table 14. TVJSC Sites Traffic Characteristics Summar~,r-Nor~east Sector NEIZO1 NET202 NE=03 NE=Z04 NEIZ05 NElz06 NE=Z07 NETZ08 NETZO9 NET210 NET211 NEl-212 NEl213 NUlZ14 NE=zl5 NET216 N~17 2 1 SB 1 01 So 2 1 WB(L9nel)
From page 41...
... 41 Table 15. TWSC Sites Traffic Characteristics Summary-Cenhal Sector
From page 42...
... In addition, the vehicle type, turning movement type, lane usage are also recorded Once these data were recorded by TDIP, a data file is assembled using a spreadsheet for further data reduction Table 17 gives the format of the raw data file. Further data reduction exacted traffic flow parameters such as flow rate, delay, critical gap, follow-up time, and queue length.
From page 43...
... , and total; Tt and To are average follow-up time and move-up time; %Q is the percent time where the approach has a continuous queue; AL is the average queue length; °/~;ITK, ALTO, and °/`iMTR are the percentages of heavy bucks, light bucks, and motorcycles; °/ciLT, PITH, and SORT are the percentages of leR tum, through, and right turn movements.
From page 44...
... These data need to be extracted Dom the raw data file prepared in the data reduction process. It Is important to correctly define the gap events that reflect a driver's behavior at TWSC intersections.
From page 45...
... The subject approach is northbound. PassTime Movement EnterQ FirstQ ExitQ 00:10:50 EBTH 00:10:51 WBTH 00:10:51 WBLT 00:10:25 00:10:26 00:10:51 00:10:52 WBTH Begin Gap 00:10:55 SBTH 00:09:31 00:10:30 00:10:54 00:10:55 NBLT 00:08:42 00:10:24 00:10:54 00:10:58 SBTH End Gap 00:10:58 EBTH 00:11:00 EBRT 00:1 1:02 EBRT 00:11:03 EBTH Example 3: *
From page 46...
... Gap Event Example Figure 21. Gap Event Example ~131U yam ·' 10~.
From page 47...
... These attributes include the minor street vehicle type, turning movement type, and lane usage; the begin gap vehicle's turning movement, vehicle type, and lane usage; the end gap vehicle type, turning movement, and lane usage; Me accepted and rejected gap size; the maximum rejected gap; the number of rejected gaps; the number of rejected gaps Mat are larger Man the accepted gap size, and the minor street vehicle's delay. The software further processes1he data file and extracts all of the accepted and the max~m~nn rejected gaps based on selected criteria, such as~rningmovement,vehicleWpe, and delay.
From page 48...
... The follow-up time can be also considered to be the saturation headway of Be minor street vehicles. A follow-up time is observed only under the following conditions: · He following vehicle has been queued, i.e., when the vehicle arrives at the intersection, there is already at least one vehicle in front of it; · botihof~e vehicles (i.e., He lead vehicle and the following vehicle)
From page 49...
... The same issues of defining gap events are relevant at a multilane site to detemiiIiing the "weight' to assign to mayor street vehicles approaching trom me right when considering the parameter vp in the capacity formula for a minor street left turn movement (if there are N lanes from He right, then the total through flow approaching from Me rift may be divided by the number of lanes N)
From page 50...
... Under a continuous queue condition, the departure flow rate is unequivocally t e actual field capacity of a minor stream movement or a minor street approach. However, at most sites, it is typically difficult to obsene a continuous queue in the field for a sufficient length of time to estimate capacity.
From page 51...
... While this method gives identical results to measuring departure flow under continuous queue conditions, it is not known and is Impossible to determine whether this method is valid when a continuous queue does not exist. It is possible that drivers may be more relaxed under low flow conditions with higher resene capacity (critical gap estimation methods cany the same caveats)
From page 52...
... The absorption method can be applied as long as major street volume or gap data are available. It is not necessary to measure the minor street delay or flow to apply this method except to estimate the critical gap and follow-up time.
From page 53...
... Flow measured in this manner during continuous queue conditions yields the field capacity for a given interval. The delay modeltesting process is discussed later in this report.


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