MTCF provides the ability to define a geographic region by selecting roads on a map. The information for these roads comes from the Michigan Geographic Framework. Usage of Framework comes with several caveats:
Framework changes every year as roadways change throughout the state. Crash data for any given year uses that year’s version of Framework for its road information.
A road in Framework is identified as a Physical Road (PR). PR’s may not span the entire actual length of a given road (i.e. multiple PR’s may be used). PR’s contain multiple Road Segments. The number of segments in a PR may change over time even if the actual road has not changed.
The color of a Road Segment during segment selection is assigned at random and only intended to help visually differentiate adjacent segments.
MTCF releases crash data per the close of the last year, hence selection of roads is restricted to the last year as well. However Google Maps (which provides the map for segment selection) changes more regularly per Google’s update cycle. Hence the segments available from Framework may not match the map shown from Google Maps. Additionally the names for roads in Framework also may not match names used in Google Maps.
MTCF links a crash to its PR and closest segment within its PR based on crash GPS information. If any of the crash data is missing or invalid, that crash will not be linked to a Road Segment.
Every subsequent release of crash data and associated Framework version requires all previous crashes to be linked against that version of Framework. In cases where roads have significantly changed or been removed, a crash may no longer link to its original PR. In these cases a best approximation has been attempted to match the crash to a nearby road segment. In some cases it may not be possible to accurately approximate a segment for a crash. Crashes falling into these categories note this information in the crash info window when selecting a crash in the Map Output in MTCF.
Shared queries that included Road Segments as Geographic Location will not be valid when crash data is updated with a new version of Framework.
The current version of Framework used by MTCF is noted in the footer of the Road Segment Selection tool.