Mislocated and Non-located Crashes

It was brought to our attention that for about 15 percent of crashes, base record controls can not be assigned because they are not within 15 ft of the crash sites. The research team became interested examining the potential impact of mislocated and non-located crashes on a candidate list of high crash locations.

Mislocated Crashes
Crash mislocations are primarily due to the ambiguity and/or insufficiency of the reported crash location data. Crashes occurred on county gravel roads and some urban city streets with different directions (e.g., north-east, south-west, etc.) are the most vulnerable crashes to be mislocated.

A police report, for example, indicates "16th and Main" as a crash location. Given that there are north-west and north-east 16th streets in the indicated city, the operator who enters the report data into the computer, may selectively add a direction to the street or just leave it as reported.

Other potential areas for crash mislocations are where one roadway crosses another at different locations. For example, a crash that occurred at cross section of either Lower Bewer and Douglas or Upper Bewer and Douglas in Des Moines, may be reported as Bewer and Douglas.

The mislocated crashes can be determined only by looking into the original crash reports. But, considering the fact that the number of crashes to be looked at is very high and that the possible gain from doing so is very low, this methodology to identify mislocated crashes will be very tedious and least likely recommended.

The other way to identify some of the mislocated crashes in an automated way is to use computer algorithms. The computer algorithms can be used only to determine the link crashes.

It can be concluded that mislocated crashes are to some extent randomly distributed rather than being stacked up at any point throughout the State of Iowa. The quantification of the distribution, however, requires a more extensive examination of the crash records.

Non-Located Crashes
In addition to mislocated crashes there are some crashes, which can not be located. These are crashes that either their locations were left blank or wrongfully entered by the reporting officers or operators. According to the recent Iowa DOT strategy, all non-located crashes are placed at a point called "Kansas". This point is the origin of the projection system for Iowa (UTM- Zone 15) and is incidentally located in Kansas. Previously, the non-located crashes were eliminated in the ranking scheme.