Are Howard County's speed limits too low or too high? That's one question some county officials hoped to answer when they reviewed a report of speed camera data from their vendor, Xerox State & Local Solutions.
Traffic engineers have attempted for decades to set reasonable speed limits by analyzing traffic flow, setting the limit at the 85th percentile speed of vehicles on the road — meaning 15 percent of drivers travel faster than the limit. The thinking goes that drivers set a natural limit based on perceived risk.
Unfortunately, Xerox produced a report with flawed data that repeatedly showed more vehicles speeding than the number that actually used the road.
That report suggested many of the county's speed limits were lower than the 85th percentile speed of vehicles traveling on the road. (For instance, the 85th percentile of vehicles in the 6500 block of Freetown Road traveled at 33 mph, but the speed limit is 25 mph.)
But the report's numbers can't be trusted, because county officials say Xerox lost some of the files used to compile it.
Howard County Police Chief Gary Gardner said Friday Xerox has been given two weeks to find missing data and fix the reports.
Fred von Briesen, Howard County's speed camera program director, said he hoped to use the data to see whether the cameras were effective in lowering speeds.
"When that report becomes reliable, there are some things in it that I would like to use," he said. "The 85th percentile data is one of the things I'd like to use."
Howard County Councilman Greg Fox, a Republican, thinks the speed limits on county roads deserve a full and accurate study.
"You have to wonder if the speed limits in some of these areas are correct," he said.
Note: This post has been updated.
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