MTCF provides the ability to select a region of a highway by selecting mile markers along that highway. The information for these mile markers is based on the MDOT Mile Markers dataset from the Michigan GIS Open Data Portal. Usage of mile markers comes with several caveats:
The Mile Marker dataset currently covers 22 highways in Michigan. In order for each of these highways to be used in MTCF, they must be a divided highway (to select direction).
These highways may not have actual physical mile marker at every mile point. In some cases missing markers were approximated on a map based on the location of a marker on the opposite direction of the highway.
If a highway changed from a divided highway to a 2-lane road, then those sections of roadway are not available for selection within MTCF.
If a divided highway stops and starts over a large stretch, then MTCF considers that 2 independent highways for the purpose of selecting mile markers.
Many highways overlap (e.g. business connectors) however every Physical Road (PR) must belong to a single highway. To clarify: only 1 highway will get assigned crashes for a given PR. There may be mile markers along overlapping stretches of highways, but some of those highways will appear to have no crashes along overlapped sections. This characteristic is also seen when a highway may stop and start in a city area.
Currently some Physical Roads (PR) may be split between more than 1 highway. When this happens some small stretches of a highway may be counting crashes from an adjacent highway.
All of the above adjustments to the Mile Marker dataset were improvements to allow for usage with MTCF. The highway selection may be improved in future changes to the dataset.