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MHN Coding
Several domains are coded into the MHN to specifically control for the node attributes.
Node IDs in the MHN are restricted to <= 29999 (as nodes >= 30000 are reserved for the MRN).
Of the node IDs in the MHN, 1-3632 are special nodes which refer to zone centroids. 3633-3649 refer to point-of-entries (POEs).
(From the travel model appendix) "Trip generation zones (or subzones) are the smallest level of geography used in the travel demand model. Subzones are quarter-section-sized geographies that CMAP uses for household and employment forecasting." There are 17418 subzones. A subzone of 0 means that there is no corresponding subzone for that node.
There are 3649 modeling zones. 1-3632 are part of the CMAP region, while 3633-3649 are POEs (corresponding to the node IDs). The modeling zones were built by aggregating the subzones.
The capacity zones were also built by aggregating the subzones.
| Code | Description |
|---|---|
| 0 | Unassigned |
| 1 | Chicago CBD |
| 2 | Chicago central area |
| 3 | Chicago |
| 4 | Inner-ring suburbs |
| 5 | Chicago urbanized area (IL) |
| 6 | Chicago urbanized area (IN) |
| 7 | Other urbanized area (IL) |
| 8 | Other urbanized area (IN) |
| 9 | Rural CMAP region |
| 10 | Rural Lake County (IN) |
| 11 | External area |
| 99 | Point of entry |
While physically, a road does not change throughout the day, the attributes of a road (such as the toll) might vary depending on the time-of-day (TOD). The MHN is set up so that the attributes are flexible enough to accommodate those variations.
| TOD | Description |
|---|---|
| 1 | Overnight: 8PM - 6AM |
| 2 | AM start shoulder: 6AM - 7AM |
| 3 | AM peak: 7AM - 9AM |
| 4 | AM end shoulder: 9AM - 10AM |
| 5 | Midday: 10AM - 2PM |
| 6 | PM start shoulder: 2PM - 4PM |
| 7 | PM peak: 4PM - 6PM |
| 8 | PM end shoulder: 6PM - 8PM |
Several domains are coded into the MHN to specifically control for the link attributes. A few of these domains are expounded on below.
Some roads are only open during a certain part of the day.
|Code|Description| |0|0 - N/A| |1|Unrestricted (open 12345678)| |2|AM Only (open 2345)| |3|PM Only (open 1678)| |4|Off-Peak Only (open 15)| |5|Peak/Shoulder (open 234678)|