By Erin Petenko | NJ Advance Media for NJ.com

Earlier this year, our intrepid colleagues took a radar gun on the road to test New Jersey drivers. They wanted to see how they stacked up to their reputation: Could Jersey drivers stay within the speed limit?

And drivers failed, miserably. Of the seven roads and 350 cars tested, only 7 percent were within the limit — and most of those had slowed down due to traffic, not because they cared enough to follow the rules.

So that got us thinking... What are those speed limits based on, anyway? And what if it's not the drivers who are wrong, but the speed limits themselves?

New Jersey doesn't have any road with a speed limit above 65 mph, even though 41 other states, including Pennsylvania, have roads at 70 mph or more, according to the Insurance Institute for Highway Safety.

Some major highways, like the Garden State Parkway or I-287, have sections with a 55 mph speed limit.

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But what if those limits were set based on drivers' own experience and intuition about what the speed of a highway should be? Oh, sure, you say, leave up to the speedster in a sports car.

Actually, the majority of people are pretty predictable, relying on cues — like the number of lanes, curves, obstructions and amount of development along the road — to figure out how fast to go.

Highway engineers measure the speed of hundreds or thousands of cars, then calculate the 85th percentile speed — that is, the speed that 85 percent of cars stayed below. Engineers use this as a guide to figure out how to set the speed limit, along with factors like traffic volume and roadway geometry.

"That 85 percent rule is the most efficient speed," said Steve Carrellas, the state liaison of the New Jersey chapter of the National Motorists Association. "If everyone goes that speed, you don't have to change speeds, which is safer and uses less gas."

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Star-Ledger file photo

Assemblyman Declan O'Scanlon, R-Monmouth, introduced legislation Thursday that would require the Department of Transportation and other agencies to use the 85th percentile to set speed limits.

"The belief that people travel some set level above speed limits is a fallacy," O'Scanlon said in a press release. "If you set speed limits based on sound engineering criteria people comply."

A spokesman for the state Department of Transportation, Steve Schapiro, declined comment on the pending legislation but said maximum statewide speed limits are established by the Legislature.

The DOT monitors speeds and collects data, including the 85th percentile of many roads. But the roads we looked at had a wide disparity between the legal limit and the actual common speed.

"People drive based on what they see on the road," Carrellas said. "It's wrong to think that someone else knows better than we, the vast majority, do."

We're not highway engineers, and the radar gun data we collected does not equate to a scientific traffic study. But looking over our numbers, they beg the question: Should the state reconsider raising the speed limit of Jersey highways? According to our data, the answers is a resounding yes.

A note about the data: For each road, 50 cars were measured between the hours of 10 a.m. and 2 p.m. in June. The collection did not distinguish between different directions of the highway. Because some of the cars were measured at a slight angle, the actual car speed may be a few mph faster than recorded.

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Route 1

Route 1 travelers in Woodbridge went fairly close to the proper speed limit, partly because traffic was a little heavy even at 2 p.m. Our measurements would raise the speed limit from 50 to 55 mph. The NJDOT's study of Route 1 in South Brunswick was close, clocking the 85th percentile at 60 mph.

Route 1's speeds are also limited by the high number of traffic lights and driveways to businesses on the side of the road.

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I-295

1-295 near Logan Township, in Gloucester County, was a little farther apart. We measured the 85th percentile at 79 mph, but decided to round down to be safe. That would change the speed limit from 65 mph to 75 mph. NJDOT also measured I-295 in Logan, and they found an 85th percentile of 81 mph — making the speed limit definitively 80 mph.

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Atlantic City Expressway

Once again, we rounded down our measurements, taken in Sicklerviile, from 79 mph to get a new speed limit of 75 mph, rather than the current limit of 65 mph.

A spokesperson from the South Jersey Transportation Authority, which operates the Expressway, said they have not collected speed data in years. A 1998 report found that the average speed of the Expressway was roughly 60 mph in Mays Landing, but the 85th percentile would be higher than that.

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I-95 Turnpike

On the New Jersey Turnpike in Chesterfield, 85 percent of drivers traveled under 82 mph, raising the limit from 65 to 80 mph. The NJDOT's numbers in Mercer County, the closest to our location, arrived at a similar result. The Turnpike Authority, which operates the Turnpike and Garden State Parkway, said they do not have speed data for either road.

The state may have good reason to avoid raising the speed limit that high, even if drivers demand it. Crashes at higher speeds are more deadly, said Tracy Noble, a spokesperson for the AAA Mid-Atlantic.

"You have to consider what's too fast on densely populated roads," she said. "Anybody can drive down the road these days and see people distracted. Sometimes they'll be going from over the speed limit to under it because they're texting."

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Route 55

Route 55 in Vineland would also go from 65 mph to 80 mph in our study. The NJDOT, also in Vineland, measured the 85th percentile at 78, so 75 mph might be more reasonable.

Route 55 has had issues with a high number of crashes and fatalities in the past. That would most likely be taken into consideration when deciding the speed limit, especially in a city like Vineland.

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I-287

I-287 has a 65 mph speed limit in some places, but the limit was 55 mph where we tested it in Morristown. That didn't stop drivers from acting as though the speed limit was 75 mph, with an 85th percentile of 77 mph. NJDOT looked at Harding Township in Morris County and got similar results, finding an 85th percentile of 78.

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Garden State Parkway

The Garden State Parkway would go through a drastic change in speed as well, going from 55 mph all the way to 75 mph in Clark. It's been proposed before. In January, a Change.org petition circulated calling for an uptick in speed on the Parkway.

The latest publicly available data on the Garden State Parkway was collected in 1998, while the state was studying the effects of changing the limit to 65 mph on parts of highways. At that time, the "average speed" of the Parkway in Woodbridge was 66 mph, meaning that the 85th percentile was probably somewhere above that.

Staff writers Rebecca Everett and Len Melisurgo contributed to this report.

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