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One of the folks on Crimemapping made a fine contribution today filled with "heads-up" tips when it comes to crime mapping.  Gary Lopez, a crime analyst for the Connecticut State Police, suggests....
 
        "The analysis of traffic accidents is an interesting one.  My perspective is looking at, for the most part, interstate highways.  State Police Departments as a general rule have jurisdiction for the enforcement of crime, traffic accidents, and motor vehicle enforcement on interstate highways.  In Connecticut, we are able to pick up a good "X" and "Y" for every accident.  We then take the data and run it through Spatial Analyst.  In looking at motor vehicle accidents on interstate highways you may find:
 
1.    Some traffic accident hotspots occur in very dangerous areas, ones that do not lend themselves to offering a great deal of motor vehicle enforcement.  That is to say, if you use high visibility enforcement you might be in a very congested area with high traffic volume.  The area is already hazardous and might not offer any safe area for ticketing.  Enforcement in these areas might actually contribute to accidents.  I have been told by some veteran officers the "trick" is to get people in and out of large metropolitan areas as fast as possible.
 
2.      The design of the highways and surrounding areas might have a greater effect on accidents than enforcement.  To effectively lower accidents on interstates you have to have long range plans that include all agencies that govern the highway.  I believe you will find many of the traffic accident hotspots on interstates fall right in the middle of where two or more interstate highways converge.  In Hartford for example, you have I-84 and I-91 intersecting in the middle of the city.  People have to make decisions on going north and south/east and west.  Of course in the afternoon, you have that sun in your eyes.  These types of decisions have to be made in seconds, and for those people not familiar with the area are at even more of a disadvantage.  Highway design plays a huge factor in highway accidents.
 
3.      In doing time studies of motor vehicle accidents, many are occurring at changes of shifts, and at peak times where police services are at a premium.  On interstates, especially around metropolitan areas you will find most of the accidents are occurring around 07:00 to 09:00 and then at 15:00 to 18:00.  This is the precise time people are coming home from work and children getting out from school; a time that has high demand for all police services.
 
4.    It is very interesting to plot DWI Accidents, meaning those accidents in which DWI was the cause of the accident.  You may find that your highest concentrations of accidents occur near routes going to major universities, large entertainment complexes, or perhaps to out of state jurisdictions where the drinking age might be lower or where bars stay open longer.  In these circumstances select enforcement can be effective.
 
5.    Careful consideration should be given to areas of the highway that are undergoing construction.  Police visibility should be present to get people to slow down. Strict enforcement of speed limits in these areas may yield to a lower accident rate.
 
In closing, I believe you will find the most accidents are occurring on interstates where there are very high volume of cars, little or no highway shoulders, areas that could benefit from a better design and where interstate highways meet.  The answer to a reduction to these accidents is a difficult one to find.  Giving out more tickets is not necessarily the answer." 
 
Gary Lopez
Crime Analysis Unit
Connecticut State Police