To design a lucrative speed trap, think like an African crocodile looking to maximize its wildebeest take. The crocodile stakes out a river crossing along a major migration route where thousands of animals will be forced into the water. Ideally, the banks will be steep and slippery, knocking the wildebeest off balance for an easy kill.

By the same token, the ideal speed trap is on a busy highway, at a spot where the limit suddenly drops, like a town line or construction zone. A downhill grade is good, because most drivers will speed up without realizing it.

Welcome to the world of revenue-based policing. I recently wrote about speed limits, and their impact on road safety and the research included some surprising findings – like the fact that Germany's autobahn, famous for its unlimited speeds, has a better safety record than North American highways.

Story continues below advertisement

It led to questions about speed enforcement. With some of the lowest speed limits in the developed world, Canada offers ideal conditions for police speed traps. In Ontario, for example, more than 750,000 drivers are convicted of speeding each year, generating millions in fines.

The speed trap is the vehicular equivalent of fishing in a barrel – police find spots where the limit is lower than expected, hide out with a radar gun, and rake in the ticket revenue.

"By definition, a speed trap is predatory and abusive," says John Bowman, of the National Motorists Association (NMA). "This isn't about safety. It's purely a revenue game."

Although police don't offer statistics on ticket revenue by location, speed traps are lucrative. An analysis of a speed trap on Washington state's Interstate 5, for example, found that a team of officers wrote a ticket every two minutes, for an estimated hourly take of nearly $8,000.

The design of a speed trap is based on deception. The most common locations are unmarked municipal boundaries, downhill sections where gravity creates natural acceleration, and roads with artificially low speed limits.

To see how it works, take a look at Toronto's Bathurst Street, home to an ongoing speed trap that has nailed countless drivers. Between Eglinton Avenue and St. Clair Avenue, Bathurst tilts downhill and passes over a long bridge that spans a green ravine. With no houses on either side, the road feels wide open, and the downhill grade helps a car speed up.

Then comes the sting. A police officer with a radar gun stands on the west side of the street, screened by a light pole. Behind him, hidden on a side street, is a police team that writes up drivers who get pulled over. This is a mass-production ticket factory.

Story continues below advertisement

The speed trap game can be elaborate. The National Speed Trap Exchange (speedtrap.org) documented a trap near the airport in Denver where police staked out a dormant construction site, then handed out $300 tickets to unsuspecting drivers.

In Pennsylvania, state police created a series of construction site speed traps in a program dubbed "Operation Yellow Jacket." The program got its name from its signature feature: radar-gun-wielding state troopers wore reflective vests that made them resemble highway workers.

Near Leduc, Alta., police ran a radar gun operation out of a crew-cab pickup truck parked by a section of Highway 2A where the limit drops from 100 km/h to 70 at an easy-to-miss municipal boundary.

Which begs the question: are speed limits about safety, or money? All of the experts I spoke to said speed limits are necessary, but noted that politicians often set limits that are artificially low, which helps generate ticket revenue – and makes roads more dangerous by creating wide speed differences between the fastest and slowest drivers.

As road designers and engineers know, roads have what's referred to as a "natural" speed, which is based on perceived risk. Drivers travel faster on a wide, straight road with no on-ramps than they would on a narrower one with curves and side streets.

"Motorist compliance has been studied many times," said Dr. Martin Pietrucha, of Penn State University. "If limits are set artificially low, drivers will break it consistently. Compliance is partly due to perceived reasonableness."

Story continues below advertisement

For governments, speed traps and ticket revenue are a seductive combination.

According to autoinsurance.org, speeding tickets generate more than $5-billion in revenue for North American municipalities each year. They also generate $10.2 billion in extra revenue for insurance companies, who add an average of $300 in surcharges for each ticket.

Everyone wants our roads to be safer. But do speed traps help achieve that? Bowman says the answer is no.

"Speed traps represent a conscious decision on the part of police and public officials. They have made a choice to take advantage of drivers who are driving at a safe and reasonable speed. They're not improving safety. They're raising money by taking advantage of drivers. And they're breeding disrespect for the law."

If you have questions about driving or car maintenance, please contact our experts at globedrive@globeandmail.com.

Follow us on Twitter @Globe_Drive.

Story continues below advertisement

Add us to your circles.

Sign up for our weekly newsletter.