Segmentation Data Elements

About

In order to make DDOT's LRS more useful to a variety of users, we create a variety of derivative data products to support a wide variety of usecases:

• Addressing/geocoding (MAR Geocoding)
• Asset management (Cityworks)
• Project management (Protrack+)
• Network Analysis (ArcGIS)
• Safety Analysis (MIRE, Crash Data Analysis)
• City Planning
• Sidewalk/Pedestrian Analysis
• ADA

Each one of these usecases might rely on one or more of the below LRS data products:

Block

PREVIOUSLY CALLED STREET SEGMENTS

For a city, street blocks are a very common way in which to organize and relate work (e.g. 'I need to fix a pothole on the 1600 Block of Pennsylvania Ave'). Although driveways or alleys may intersect streets, the Block segmentation requires that the segment remain unbroken.  A block will always begin at a street-to-street intersection and end at the next street-to-street intersection. 

Road Types included:

• Streets

Segmentation Rules: 

• Only Streets can break/segment other streets.
• Only At-grade type intersections are respected in this segmentation.  See below for more information 

Block Attributes

{962C2785-EE57-4B19-AEE9-D18CB5C30870}

SubBlock

PREVIOUSLY CALLED ROADWAY SEGMENTS

SubBlock represents the full extent of our centerline network.  SubBlock is the finest-grained, 'base' segment from which all other segmentation patterns can be constructed (including Blocks).  SubBlock is the original source features for our DDOT Street Centerlines data

Road Types included:

• Streets (Code 1)
  
• Alleys (Code 2)
  
• Ramps (Code 3)
  
• Service Roads (Code 4)
  
• Trails (Code 5)
  
• Driveways (Code 6)
  
• Walkways (Code 7)

Segmentation Rules: 

• Streets, alleys, ramps, service roads and trails can break all others roadway type segments.
• At-grade type intersections are respected in this segmentation.  See below for more information 
  
  

SubBlock Attributes

Intersection Approach Segments

Intersection Approach Segments are short segments of the route that approach an intersection, in other words, a short section of the road leading up to an intersection.

Structure of Approach Segments

Fig 2. Approach representation

Understanding Approach Intersection Direction

Intersection direction can be a confusing attribute to understand.  Its core purpose is to provide the network direction flow to the intersection point. (for each individual intersection approach)

When paired with cross-section data, this attribute gives the ability to determine if sections or lanes are approaching or departing the intersection.  This may be especially important in safety analyses (such as LTS) which focus primarily upon lane and sections which are approaching (not departing) an intersection.  See Fig 3 for a graphic diagram.  

Intersection Approach Attributes

Blockface Segments

Blockface Segments are unbroken sections of the curb. A blockface can be made up of several subblocks, or just one subblock. Blockfaces are directional, so there will be segments on both sides of the road, each dependent on an unbroken length of curb.

Blockface segments are one of the core elements of the ParkingZones, since

Blockface Attributes

SubBlock Intersections 

Intersections are automatically created, however they are not singular points.  The LRS creates a series of points - one for each intersecting road at that intersection.  For DDOT, it is more useful to have a single intersection point representing a given intersection.  Through a custom DDOT script, the collection of overlapping intersection points is reduced into a single representative point and this is our SubBlock Intersections Layer.  

SubBlock Intersection Attributes

Intersection Grade Codes

IntersectionRoutes

IntersectionRoutes is a 1-to-many related table to SubBlock Intersections.  For each SubBlock Intersection, IntersectionRoutes contains 2 or more records - one for every intersecting route occurring at that location.