SIOUX CITY | Rear-end crashes have increased at five of eight Sioux City intersections where red-light cameras were installed, state data obtained by the Journal show. Police say the devices are making the roads safer overall.
They also agree with state transportation officials and others who have said it's difficult to draw conclusions about the effectiveness of the city's red-light cameras because the systems have been in place for only a few years. Most of the intersections had a small number of crashes, which can skew percentages with little change in actual numbers.
Such variables as increased traffic flow, changing traffic patterns, weather and road construction affect the number of crashes from year to year at any intersection, making it hard to compare those statistics, said Sioux City police Capt. Melvin Williams.
Sioux City has 11 red-light cameras at nine intersections and two speed cameras in Interstate 29 construction zones.
Experts say jurisdictions can expect an increase in rear-end collisions when they install red-light camera systems at the same time the systems reduce more serious, costly accidents.
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In Sioux City's case, new police data obtained by the Journal show a 40 percent decrease in crashes from motorists running red lights at intersections with cameras and a 15 percent reduction in all crashes. Iowa Department of Transportation data also show a decline in accidents involving red-light running.
"In general, this is a positive result, as rear-end crashes (though not desirable) are not as severe (or dangerous) as right-angle crashes that might otherwise occur," David Levinson, professor of transportation engineering at the University of Minnesota, said in an email.
University of Missouri-St. Louis transportation studies professor Ray Mundy said rear-end crashes typically increase after systems are installed and drivers slam on the brakes when they see the camera flash. Such accidents usually decrease over time as people get used to driving through camera-controlled intersections.
He echoed Levinson in saying more slower-speed rear-end crashes are a tradeoff for reducing higher-speed, T-bone crashes that happen when drivers run red lights.
Mundy also pointed out that it will take more years of statistics to determine how effective the cameras are in improving safety.
Sioux City started its traffic camera program in 2009, when it installed devices at Cheyenne Boulevard and Outer Drive, Fifth and Court streets, Gordon Drive and Fairmount, Nebraska, Palmetto and Pierce streets, and Sergeant Road and Lakeport Street.
Cameras were added at Lewis Boulevard and Outer Drive in 2010.
Police installed cameras at Singing Hills and Lewis boulevards in November 2013. Data from that intersection were not included in the Journal's analysis because they show only one month of red-light camera operation.
IDOT information shows the average number of rear-end crashes increased after cameras were installed at five of the eight intersections. The number went down at the Gordon Drive intersections with Pierce and Nebraska streets, and there was no change at Fifth and Court streets.
Overall, rear-end crashes increased 16 percent at intersections outfitted with red-light cameras in 2009.
They increased at Lewis Boulevard and Outer Drive by 91 percent, from an average of 0.33, or less than one per year, before the cameras were installed to 3.5 per year after installation.
However, police note traffic there increased by approximately 13,000 vehicles per day after the Irving F. Jensen Bridge opened in 2010. The bridge spanning a series of railroad tracks takes drivers from Lewis Boulevard to Floyd Boulevard, both busy thoroughfares.
"Do you have a potential increase in accidents because of that? Absolutely," Williams said. "Is that then the fault of the photo enforcement being there? Heck no. If anything, the photo enforcement lowered the increase."
The Sioux City Police Department on Wednesday submitted its own data about the cameras to the IDOT. The state agency required all municipalities using automated traffic cameras to submit information by May 1 to justify the systems' continued use on state roadways.
The city asked a judge to throw out the new regulations, but state officials resisted. The case is set for a hearing May 12 in Woodbury County District Court.
Despite the complexity of attempting year-to-year comparisons, police credit the cameras with increasing safety and driver awareness throughout the city. They point to an overall decline in crashes at red-light intersections, fewer crashes from running red lights, fewer violations and less-severe crashes on I-29 since the cameras were installed.
"Every time somebody runs a red light, somebody else is put at risk," Williams said. "So, the number of the times we lower the red-light running, it lowers the number of times an innocent family is put at risk."
The University of Minnesota's Levinson agreed the decrease in red-light crashes showed the systems improved safety.
"That is the important takeaway," he wrote.