We have recently been adding features to our Collision Database Management System to better handle client jurisdictions with large numbers of collisions. The first new feature is a preview results button for general queries. Before displaying a full results page that includes a list of all collisions, tables and charts, and a map, the preview results shows key summary statistics. The preview includes total collision counts, total victim counts and breakdowns of the collisions by severity, type and motor vehicle involved with:

preview results

Often times these key summary statistics may be all a user is looking for and this will provide quick results for copying/pasting into other documents. For the application usability, it helps us to prevent excessively large queries from going to the results page. This is important since loading too many results will significantly increase the memory in the web page, slowing down your whole web browser. The map view is not designed to show 30,000 points at once and restricting to only viewing clusters or a heat map is not conducive to analyzing collision data. It would be better to download the complete collision datasets and use desktop GIS software to analyze that many points.

You may also notice that we enforce this limit by disabling the results window until you have clicked the preview features button. We currently set the limit at about 15,000. This encourages you to use other filters to narrow your search down to a more reasonable number. Of course in a large city, you may be interested in all collisions over several years, but only in a particular area. Until now the other filters would not have been of any help in this task. The new spatial and corridor query filters take care of this scenario and I will detail them in the next blog post.

In the meantime, you can try out the preview features button for any general query.

Co-Founder of RoadSafe GIS. Bringing collision data, GIS and cloud technology together. Formerly of UC Berkeley SafeTREC and ESRI.