The Venturi effect and traffic flow: Why cars go faster on one-lane roads

By Scot Morris
Del Mar

With the campaigns on Proposition J being argued back and forth, there has been some confusion on the issue of traffic flow on one-lane vs. two-lane roads.

I hate driving at rush hour. Going north on Highway 101, down Torrey Pines hill toward Del Mar, I clocked myself on this two-lane road, at the glacial pace of just 15 miles per hour. I knew that halfway between the bottom of the hill and light at Carmel Valley Road, the road was going to constrict to one lane, and I resigned myself to slowing even more.

To my surprise, when traffic merged into one lane, my speed doubled to 30 mph!

How can this be? Physics. It’s because of a principle called the Venturi Effect: The velocity of a fluid increases as the cross-sectional area decreases. You see this with your garden hose: Put your thumb over the opening (constricting the flow) and the water speeds up enough to go over the hedge.

The same principle is at work on Highway 101, especially at some distance from the light at Carmel Valley Road. If you add stop signs and stop lights to a road the flow halts and starts up again, so the Venturi effect is less noticeable.

But the fact remains: If, on a two-lane road, traffic flows at a given speed with X cars going by per minute, those same X-cars-per-minute must go twice as fast on a one-lane road!

Strange but true. If you doubt me try it yourself.

Related posts:

  1. Studies show Prop J will improve traffic flow
  2. Roundabouts can improve traffic flow in many ways
  3. Don’t make traffic problems worse; Vote ‘No’ on Prop J
  4. Passage of Prop J will cause excessive traffic congestion
  5. One Paseo: Traffic jams for Carmel Valley

Short URL: http://www.delmartimes.net/?p=41856

Posted by Staff on Oct 30, 2012. Filed under Letters, Opinion, Uncategorized. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

Leave a Reply

Archives

Facebook

Bottom Buttons 1

Bottom Buttons 2

Bottom Buttons 3

Bottom Buttons 4

Bottom Buttons 5

Bottom Buttons 6

LA JOLLA NEWS

RSS LA JOLLA NEWS

  • Berkshire Hathaway HomeServices’s La Jolla office tops in real estate sales volume for first half of 2014
    Berkshire Hathaway HomeServices reported its La Jolla office was No. 1 for sales production through the first half of the year, out of the company’s North American network of offices. The results point to another year of dominance for the La Jolla office, which has ranked No. 1 nationwide for nine of the last 11 years. […]
  • House of Week; 329 Bonair Street #4
    Buy The Sea! 3 bedrooms, 3 full baths. Just a 1/2 block to famous WindanSea Beach. Watch for the green flash in the sunset from one of 5 balconies. Over 1350 sq ft. Great separation of bedrooms. Marble living room fireplace. Skylights. Dual pane windows. Gas range. Two-car tandem garage off alley. Offered at $995,000 […]
  • What were the odds?
    I think we’d all agree that no one should have to worry about being run over by a motor vehicle in their own shower. I’m a world class worrier but until it almost happened, it never occurred to me to worry that a stolen car would crash through our front fence and stop inches from joining me in the master bath. This wasn’t recent, fortunately, but it comprise […]

RANCHO SANTA FE NEWS

RANCHO SANTA FE NEWS

RSS RANCHO SANTA FE NEWS