Combining Crash and EnforcementLocation Data to Determine Selective Enforcement Strategies

4th Annual GIS Symposium - TroyNovember 16, 2007

Outline

• Data sources• Starting point • Mapping crashes (points, lines, regions)• ECitation• Mapping citations (points, lines, regions)• Hot and cold zones• Process summary• Future plans• Bonus material

Data Sources

• Crashes– Paper crash reports (ECrash)

– Mapable by route & milepost– Three month lag on most crashes– Complete Alabama data for past 15 years

• Citations– ECitation– GPS – Two to three day lag on most citations– State trooper and some municipalities (Oldest data 2002)

• Officer Locations– Real-time for some troopers– Plan to recorded positions periodically

Starting Point

• The questions– When & where should officers patrol to

reduce fatalities and serious injuries?– How is “the answer” best presented? – How should recommendation effectiveness

be assessed?

• Conventional wisdom:– Position enforcement operations in high

crash locations (“hotspots”)

Crash Points4 years of mileposted crashes

CrashesPer

TrooperPost

• Five-mile segments

• Reflect overall activity within a particular segment

• A coarser-grained look at activity than simply displaying individual crashes

Segments Instead of Points

Crashes as Graduated Lines

Other Ways to Slice

• Look at subsets of crashes:– Fatalities– Injuries– Alcohol– Etc.

• Overlay other types of data:– Traffic volume– Roadway characteristics– Enforcement patterns

Electronic Citations in Alabama

• Initiated in June 2002• Approximately 420,000 transactions to date:

– 360,000 citations– 60,000 warnings– 1700 transactions per day

• Deployment– Most state troopers (around 450 officers) – 91 officers at 10 local agencies – 46 agencies in progress

• Real-time citation GPS locations

Citation PointsGPS

Citations Citations Per PostPer Post

Citationsas Graduated Lines

Hot & Cold Zone Designation

Computing Hot/Cold Zones

• Based on trooper post• Hot zone - 5-mile segments where:

– Crashes exceed the post average for crashes– Citations are below the post average for citations

• Cold zone - 5-mile segments where:– Citations exceed the post average for citations– Crashes are below the post average for crashes

• A possible officer deployment strategy:– Route officers to hot zones– Route officers away from cold zones, except where they overlap

hot zones

Above and Below Post-Average-CrashesPer 5 Mile Segment

Mobile Post

Above and Below Post-Average-CitationsPer 5 Mile Segment

Mobile Post

Hot & Cold ZonesHot Zones

Below Average CitationsAbove Average Crashes

Cold ZonesAbove Average CitationsBelow Average Crashes

Process Summary

Next Step

• Need to implement enforcement decisions based on this strategy

• Need to monitor the effectiveness of shifting resources:– Does reducing citations negatively impact a low-crash coldspot?– Does increasing citations positively impact a high-crash

hotspot?

• Based on the results of this evaluation, continue to shift resources

• Ultimately:– Make enforcement decisions based on data, not feel

Future Plans

• Data quality and timeliness:– Obtain 85-90% of citation data electronically (with GPS

coordinates)– Obtain real-time crash data with GPS coordinates using ECrash

• Incorporate officer location data– Analyze crashes and citations and officer patrol locations

• Identify routes, not just locations• Develop more sophisticated algorithm for identifying hot

& cold zones

Questions?

• Contact information– dsteil@cs.ua.edu