Route_ID
Route_ID is the unique route identification number for the LRSN_Routes feature class in our Roads and Highways geodatabase.
Field Type Text
Field Length 255
Format 00000000000
Route_ID is created by concatenating the values from the following 4 fields from the LRSN_Routes feature class:
1. Route_Location_Code characters 1-3 (left to right)
2. Route_Number characters 4-7
3. Route_Type characters 8
4. Qualifier characters 9-11
The values applied to constituent fields for each Route_ID are described below.
Route_Location_Code – The route location code identifies the general area in which a given route is located. We investigated using existing boundary data sets (boroughs, census areas, maintenance districts…) for the route location code but Alaska lacks data that is both stable and granular enough for these purposes. Instead, we created three separate polygon feature classes to help us parse up the road network, they include: remote areas, accessible areas, and highway corridors. Polygons from each feature class were sequentially numbered from south to north based on the centroid latitude. Only even numbers were applied to leave room for the creation of additional features in the future. The location code numbers were then transferred to the routes using the Identity GP tool. Each route location code feature class is briefly described below.
1. REMOTE_AREAS – Routes in remote areas, only accessible by plane or ferry, have a location code value between 400 and 999 (figure 1). Because of the large number of remote areas, we developed an additional polygon feature class, Regions, to help us group and code the remote areas (figure 2 and figure 3).
2. ACCESSIBLE_AREAS – Routes in areas accessible from the State’s contiguous road system have a location code between 200 and 399 (figures 4 and 5).
3. HWY_CORRIDORS – Routes that represent a major highway or a route that is connected to a major highway, and is not covered by the other two location categories, have a location code between 100 and 199 (figure 6 and 7).
Route_Number – The routes (within each location code area) were assigned a four digit number based on order in which the records are stored in the routes feature class. This approach should simplify the task of assigning route numbers to newly added routes.
Most of the route numbers were adjusted to start at 1,000 and increment by 1. The exceptions to this rule are:
1. Major highways which are set to 0000
2. The non-inventory side of divided highways, routes associated with a grade separated ramp complex, a very small number of at grade ramps, and traffic circles. These features are given the same route number as the route they are most related to, however, they are also assigned unique Type and Qualifier values to help distinguish them from their relatives. For example, the Seward Highway has a route ID of 102-0000 and Southbound Seward Highway is assigned 102-0000-D-1.
Route_Type – Route type is used in a small number of cases to help relate or differentiate routes. We are currently proposing the following route types:
1. X – roadway
2. C – traffic circle/roundabout
3. D – non-inventory side of divided highway
4. F – off ramp (associated with a grade separated ramp complex)
5. I – inventory side of divided highway
6. N – on ramp (associated with a grade separated ramp complex)
7. R – at grade ramp (not associated with a grade separated ramp complex)
8. S – slip ramp (associated with a grade separated ramp complex)
9. P – spur
The sample data includes examples of all of these Route Types with the exception of traffic circles/roundabouts. These were excluded because they are not correctly modeled in the current data.
Route_Qualifier – Qualifier values are used to ensure that the route IDs of related features are unique. In the case of ramps, the values also help identify the features that participate in a given ramp complex. Figure 8 shows the route IDs for the Seward Highway, Tudor Road, and the related ramps. The Seward Highway and the ramps all share a common route number and the Type and Qualifier values help differentiate them.
In the sample data we reserved a range of 10 route numbers for each ramp complex. Individual qualifier numbers were applied in a counter clockwise direction starting with the ramp in the inventory direction with the lowest milepoint value. Should a new ramp complex be added between existing ramp complexes we would not try to add qualifier values that would fit the sequential gap. Instead, like the route numbers, we would simply look to the next available range of numbers available and use those.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8