Lawmakers fall all over one another trying to pass new laws that will prevent more fatal motor vehicle accidents. That’s why seat belt use is mandatory, why drivers and passengers are effectively surrounded by air bags and why sending a text message while driving is now both incredibly stupid and illegal.

But there already is a law that, if followed, could reduce by thousands the number of fatalities in the country. Maybe you’ve heard of it: It’s called the speed limit.

During a two-day period last month, three young women were killed in car accidents. The fact that the driver in one case had been drinking and in the other may have been texting got most of the attention. In both cases, police believe the drivers also were speeding.

That shouldn’t be surprising. Speed is a contributing factor in about 30 percent of all fatal crashes, according to the National Highway Traffic Safety Administration. In 2006, more than 13,500 people died in speeding-related motor vehicle crashes.

Those new antitexting laws aren’t about to change that.

Here’s an experiment for you to try: If you drive on one of the region’s many expressways for your daily commute, head for the right lane and try to drive at the speed limit. If you’re on the 400 or the 990, shoot for 65. On the Youngmann, go 55. If you’re on the Kensington, go 50. (Yes, 50, not 55 and not the very popular 85.) Then count the number of vehicles that roar past you. (For extra fun, count the number of times you see flashed headlights in your rearview mirror and the number of middle-finger salutes.)

Where else but behind the wheel is there such enormous pressure to break the law?

Yet, mathematically, it doesn’t make a lot of sense to drive, say, 70 mph in a 55-mph zone. Even if you’re headed somewhere 15 miles away, driving that fast would get you there only about 2 or 3 minutes sooner. And the financial cost of getting caught would seem to outweigh the slight amount of time saved.

Tell that to the 100 or so people sitting in Amherst Town Court last week to hear from Town Justice Mark Farrell. The majority were there for speeding tickets. For the benefit of going a little faster, their wallets were lightened by $100 or more—sometimes a lot more— and they were forced to spend hours of their day settling their case.

Farrell has a well-deserved reputation as a judge who is interested not only in punishing bad behavior, but changing it. It’s why he runs a domestic-violence court, a drug court and the only gambling court around. So when he deals with speeders, he is not content to give everyone a plea deal, collect their money and send them on their way, as some judges are. As a result, many repeat offenders in Amherst end up with points on their license or doing community service or at least spending four hours in a local high school taking a refresher driving course as part of their plea deal.

“What’s the point of giving people repetitive slaps on the wrist and not sending a message with regard to speeding and what it can lead to?” Farrell said. “It’s sometimes accompanied by . . . just plain stupidity and recklessness or indifference to other people. Speed seems to be the singular cause of a lot of difficulties.”

Sometimes that difficulty costs a person some time and money. Sometimes, as in the cases last month and thousands every year, it costs people their lives.

Either way, it’s not worth it.