Eliminating Left Hand Turns

These studies will have areal impact on street design and planning.  The bottom line is that left hand turns are hugely inefficient during periods of heavy traffic and need to be diverted into right turn loops.  The saving on fuel experienced by myth busters is actually a shocking result and informs us just how much fuel is spent idling while waiting for a traffic signal.

Fundamentally we need to stop catering to the left hand turn and spend of making the alternates work well.  This means improving the available right hand turn corridors so that the traffic can use it smoothly.  It may seem an inconvenience to drivers who want to go left but we now know better and should we think on it, idling in a left hand turn lane while waiting for a traffic opening has always been problematic.

The direct saving in both fuel usage and accident rates provide a direct incentive to reengineer all such busy streets and theirs feeders.  I know from experience that there are plenty of locations were doing a right hand turn is not particularly practical and this will take time to fix if it can be done.

Yet beginning with the easy ones will allow us to educate the public.

Obviously this clearly applies to heavily traveled streets and not your typical residential street network.  however, fixing all this will impact on a lot of residential streets to some degree.

Eliminate left turns to achieve 20% faster travel times on surface streets

JANUARY 10, 2011

http://nextbigfuture.com/2011/01/eliminate-left-turns-to-achieve-20.html

The so-called “superstreet” traffic design results in significantly faster travel times, and leads to a drastic reduction in automobile collisions and injuries, according to North Carolina State University researchers who have conducted the largest-ever study of superstreets and their impacts.

Superstreets are thoroughfares where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare. In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median. While this may seem time-consuming, the study shows that it actually results in a significant time savings since drivers are not stuck waiting to make left-hand turns or for traffic from cross-streets to go across the thoroughfare.

* a 20 percent overall reduction in travel time compared to similar intersections that use conventional traffic designs

* superstreet intersections experience an average of 46 percent fewer reported automobile collisions – and 63 percent fewer collisions that result in personal injury



US motor vehicle deaths by year

2005   43,443  

2006   42,642 

2007   41,059

2008   37,261 

2009   33,808  

About 90-115 people die every day in vehicle crashes in the United States. 

Worldwide an estimated 1.2 million people are killed in road crashes each year and as many as 50 million are injured. Projections indicate that these figures will increase by about 65% over the next 20 years unless there is new commitment to prevention.

There is the potential that widespread superstreet adoption would save several thousand lives per year in the USA and a few hundred thousand lives worldwide.

The paper is called Operational Effects of Signalized Superstreets in North Carolina.

Mythbusters showed that only using right turns saves gas

Here is an online article that analyzes the Mythbuster show on right turns versus left turns

The myth was setup from the perspective of a delivery truck driver. Several locations within the San Francisco area were setup as delivery points, then two routes were derived. The first route was a more “logical” route trying not to favor right turns. This route had eight left turns, four right turns, and a total distance of 5.2 miles. The second route tried to exclude as many left turns as practical. The “right turn” route was 6.8 miles long, had one left turn and twenty-three right turns. Each route visited each stop in the same order.

The MythBusters concluded that right turns were indeed more efficient in their test. While the route favoring right turns was a longer distance and took a longer amount of time, it used only 4.0 gallons of fuel compared to 6.8 gallons of fuel on the “control” route.

No Left Turn: ‘Superstreet’ Traffic Design Improves Travel Time, Safety

http://news.ncsu.edu/releases/wmshummersuperstreets/

Matt Shipman | 

Dr. Joe Hummer |

Release Date: 01.10.2011

Filed under Releases

The so-called “superstreet” traffic design results in significantly faster travel times, and leads to a drastic reduction in automobile collisions and injuries, according to North Carolina State University researchers who have conducted the largest-ever study of superstreets and their impacts.

Superstreets are surface roads, not freeways.  It is defined as a thoroughfare where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare. In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median. While this may seem time-consuming, the study shows that it actually results in a significant time savings since drivers are not stuck waiting to make left-hand turns or for traffic from cross-streets to go across the thoroughfare.

"Superstreet" traffic designs result in faster travel times and significantly fewer accidents, according to the new study.

“The study shows a 20 percent overall reduction in travel time compared to similar intersections that use conventional traffic designs,” says Dr. Joe Hummer, professor of civil, construction and environmental engineering at NC State and one of the researchers who conducted the study. “We also found that superstreet intersections experience an average of 46 percent fewer reported automobile collisions – and 63 percent fewer collisions that result in personal injury.”

The researchers assessed travel time at superstreet intersections as the amount of time it takes a vehicle to pass through an intersection from the moment it reaches the intersection – whether traveling left, right or straight ahead. The travel-time data were collected from three superstreets located in eastern and central North Carolina, all of which have traffic signals. The superstreet collision data were collected from 13 superstreets located across North Carolina, none of which have traffic signals.

The superstreet concept has been around for over 20 years, but little research had been done to assess its effectiveness under real-world conditions. The NC State study is the largest analysis ever performed of the impact of superstreets in real traffic conditions.

A paper on the travel time research is being presented Jan. 24 at the Transportation Research Board Annual Meeting in Washington, D.C. The paper is co-authored by Hummer, former NC State graduate students Rebecca Haley and Sarah Ott, and three researchers from NC State’s Institute for Transportation Research and Education: Robert Foyle, associate director; Christopher Cunningham, senior research associate; and Bastian Schroeder, research associate.

The collision research was part of an overarching report of the study submitted to the North Carolina Department of Transportation (NCDOT) last month, and is the subject of a forthcoming paper. The study was funded by NCDOT.

NC State’s Department of Civil, Construction and Environmental Engineering is part of the university’s College of Engineering.