Referencing Traffic Data on a Linear Referencing System

Transcription

1 Referencing Traffic Data on a Linear Referencing System Kent L. Taylor, P. E. North Carolina Department of Transportation

2 What is an LRS? Linear related to a line Reference provides a method to locate something in relation to a line

3 What is an LRS? Highways are linear > they are a network of lines The method is the challenge Is there method to our madness?

4 LRS Basics Begin Line Segment (Arc) Direction End This is the linear part!

5 LRS Basics Referencing Begin Measure Offset End Traffic references usually do not require offsets

6 Traffic References Collection Elements All traffic counts are collected at points on the highways Station ID Reporting Elements Traffic data are used on segments for HPMS and other purposes Station ID

7 Traffic References Collection Referencing Arc ID Station ID Measure Reference = Arc ID, Measure, Station ID

8 Traffic References Reporting Referencing Arc ID From Station ID To Reference = Arc ID, From, To, Station ID

9 NCDOT LRS Factor = Partial Arc Length From Begin Total Arc Length LRS Arcs Arc ID Direction End Factor = 1 Begin Factor = 0

10 NCDOT LRS Divided Highways > Dual Carriageway Non-Inventory Direction Inventory Direction Direction of Increasing Mileposts

11 NCDOT LRS LRS Arcs for Divided Highways Arc direction matches traffic flow direction Traffic is referenced on the inventory arcs Arcs for each carriageway

12 Traffic Referencing Rules AADT has the highest resolution Primary referencing is done on AADT Other traffic is attributed on AADT Other traffic attributes can t split AADT We maintain AADT on the LRS arcs then update other traffic attributes on AADT

13 Collection Elements Referencing Traffic on an LRS Traffic Referencing Process C1 V1 V2 C2 V3 C3 V4 V5 V6 C4 = PTC (AADT) = PVC (Class) Reporting Elements AADT HPMS >> All FC Down to Collectors NCDOT >> Traffic Flow Business Rule Class segments never bisect an AADT segment Trucks HPMS >> NHS NCDOT >> Primary Routes Collector Local SR SR NC Principal Arterial US Minor Arterial

14 Traffic Referencing Process C1 V3 V4 C4 A1 A2 A3 A4 A5 A6 C1 C4 Traffic Segments References for Traffic Segments AADT C1 V3 V4 C4 VC C1 C1 C4 C4 LRS Arc From To AADT VC A1 0 1 C1 C1 A2 0 1 C1 C1 A3 0 1 V3 C1 A4 0 1 V4 C4 A5 0 1 V4 C4 A6 0 1 C4 C4

15 Traffic Referencing Process Collection Elements 42,000 Volume 4,500 Ramps 3,500 Class 50,000 Collection Elements

16 Referencing Traffic on an LRS Traffic Referencing Process Reporting Elements 28,500 Traffic Segments (AADT) 70,000 Traffic Referencing Arcs Utilizing Geo-R eferencing to Enhance the Value of Data

17 Quarterly Update Process Resources used in this process are: Migrated traffic references Traffic references that failed to migrate LRS Arc changes Roadway attribute changes Resolving these issues synchronizes the data and ensures proper monitoring

18 LRS Arc Changes Traffic references are migrated using the LRS event data Those that fail to migrate are flagged LRS Arc changes from one quarter to the next are audited for: Additions Deletions Modifications

19 Roadway Attribute Changes Changes in attributes are checked for: Functional Class - Local>+FC; +FC>Local Routing - change in inventory direction Couplets - requires non-inventory NHS - requires class monitoring Truck Routes - class monitoring This identifies changes needed in how we reference and where we monitor

20 Referencing Results References can be used in 3 ways: Spatially synchronized with LRS Arcs for spatial relationships LRS References event data for relating with other data referenced on the LRS Route/Milepost event data for relating with other data referenced using this method Route/Milepost is an attribute added using the LRS Arc references after updating

21 Quality Control Check the linear references by: Topology Rules identifies overlaps and gaps in routes required to be referenced Dynamic Segmentation use event data to find inappropriate combinations of attributes Check the traffic references by: Validate station IDs with inventory tables Check AADT stations for more than one VC

22 Generating Traffic Products Depends on the needs of the customer: Large Scale provide LRS references without dissolving and attach traffic data needed; served by GIS files and tables Small Scale Simplify data by dissolving then attach the data; simple for manual retrieval; mapping services in Spatial Data Viewer (SDV)

23 Generating Traffic Products Two Step Process: 1. Dissolve 2. Attach

24 Supporting HPMS Traffic Data PTC PVC ATR WIM Proj. Traffic Data Production Lines Collection Analysis Reporting Collection Analysis Reporting Collection Analysis Reporting Collection Analysis Reporting Collection Analysis Reporting Staging Tables LRS Production Lines Collection PTC PVC ATR/WIM Reporting AADT CLASS Traffic Data Submit_Sections Coverages AADT AADT SU Route_Shapes Other Sections NHS Submit_Sample_Sections Samples AADT MU Samples AADT SU K Factor Peak SU Dir AADT MU Fut AADT Peak MU Table Of Potential Samples - TOPS AADT Facility Type Urban Code Functional System Through Lanes

25 Thank You! Questions? Kent Taylor (919)