The evolution of the NJDOT Automated Straight Line - GIS-T

Creating Value …
… Delivering Solutions
Advanced Linear Referencing for
Transportation Data M odels
Presenter
• Justin Furch
• Project Manager
Agenda
• Definition of Linear Referencing
• How Linear Referencing is used in
Transportation
• Various LRS models
• NJDOT hybrid model
• The future…
What is a LRS?
• LRS = Linear Reference System
• A one-dimensional means to locate
information along a linear system.
• Uses a linear identifier and
measure(s).
Why use LRS?
• LRS is a convenient format
– Ex. An accident occurred at “Rt. 1, milepost 12” vs.
“1659060.25, 1525238.97”
• Works well for linear networks:
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Roadways
Bus lines
Trains
Pipelines
Waterways
Utilities
LRS beginnings in Transportation…
• Predates Transportation GIS
• Implemented as
hand-drawn
Straight Line
Diagrams
How Transportation LRS is utilized…
• Field Crew inventory
How Transportation LRS is utilized…
• Straight Line Diagrams
Linear Referencing role in GIS
• LRS compliments GIS, showing locations along a
centerline using GIS “line events”
• LRS works well with linear networks, including
transportation related features and assets
Examples of Transportation LRS data
• To describe incident locations such as accidents.
– Locating accidents:
• To describe roadway characteristics, such as lane
count, speed limit, pavement width, etc.
– Temporal Pavement Quality:
Types of LRS Features
• Point features:
– Uses a route identifier
and a measure field
• Linear features
– Uses a route identifier and two measure fields (to-from)
Various LRS model
• Single Centerline Model
• Dual Centerline Model
The original single centerline model
• Roadways represented as traditional “Routes”
• Follows historical route paths
Single Centerline Model:
• Advantages
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Aligns with historical data
Easy to describe relative roadway locations
Translates easily to field mile-marker signs (when available).
Works well for low-detail mapping
• Disadvantages
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Over-simplified view, in-flexible and non-scalable
Ambiguous GIS centerline definition
Cannot accurately describe true distance measures
Problematic with detailed roadway inventory
The dual centerline model…
• Separates the road based on physical separation:
– Pavement edge, grass median
– Physical barrier
• Distinct road
designations for
each segment
Dual Centerline model:
• Advantages:
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Follows physical roadway geometry
Follows the cartographic representation of the road
Allows for separate attributes per divided segment
Can accommodate actual roadway measures
• Disadvantages:
– Complex, requiring specialized software
– Difficult to translate to a traditional route model
NJDOT’s hybrid design…
• Multi-centerline design (accommodates divided and
local/express lanes)
• Includes additional attributes to allow data to “roll-up”
to a single centerline LRS.
How does this model work?
• Uses “parent” fields to create a hierarchy
(self-joined LRS)
Advantages of this model
• Allows for multi-centerline functionality
• Allows multi-centerline segments to roll-up
• Roadway data can be used in single or multi-centerline
format by using “rubber-banding” techniques
• Actual measures can be used.
An example:
Systems supported by this model:
• Leveraging multi-centerline:
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NJDOT Straight Line Diagrams
NJDOT Roadway Video Log Application
NJ Highway Maintenance Management System (HMMS)
GIS NJ Roadway Network
• Leveraging single-centerline:
– NJDOT Highway Performance Monitoring System (HPMS)
– NJDOT Traffic Monitoring System (TMS)
In Conclusion…
• Developing a hybrid centerline model has allowed
NJDOT to leverage new inventory techniques and
accuracy, while retaining the existing legacy data and
format.
The future of NJDOT’s LRS?
• Enhanced model that
includes more then two LRS
models
Questions?...