Georgia DOT takes traffic light timing regional | ajc.com

DOT takes traffic light timing regional ajc.com The Georgia Department of Transportation will be taking a regional approach to traffic signal timing.

Christie to Refinance Transportation Trust Fund Bonds in October

Many states are dealing with the same issue. Past borrowing must be repaid out of current gas tax revenues, which are decreasing due to the economic downturn.

NJ Spotlight Christie to Refinance Transportation Trust Fund Bonds in October: "The last borrow-and-spend decision came in March 2006. Two months after taking office, Democrat Gov. Corzine and Democratic legislative leaders agreed on a plan to refinance TTF debt from 21 years to 31 years and to use the new borrowing to provide $1.6 billion a year in state matching funds for new transportation projects from FY 2007 through FY 2011. They knew that as of July 1, 2011, every penny previously dedicated to the fund would go simply to pay off past debt. But they were not worried because they fully expected to vote to raise the gas tax after Corzine’s reelection."

Behavioral Economics Offers Insights and Strategies for Improving Transportation

An interesting article about using human behavior to create safer transportation environments. the main point I take away from this article is that most traffic engineers view drivers (and pedestrians/bicyclists) as acting completely rational when making decisions and plan/design based on this assumption. In actuality, the users of the transportation system can act irrationally or counter intuitive. Understanding human behavior can lead to unconventional solutions that cost a fraction of physical improvements.

My favorite is the use of perpendiculair lines to reduce speeds in Chicago:

Notice that the space between lines gets smaller. This creates the preception that your speed is increasing causing you to slow down. According to Chicago DOT, crashes have been reduced 36 percent.

Diverging Diamond Interchanges

One of the most innovative interchange concepts to come along in the past few years is the diverging diamond interchange (DDI). It is also called a "double crossover diamond" interchange by FHWA. The concept originated in France. There are currently 2 open to traffic in Missouri, one under construction in both Tennessee and Utah.

A DDI design requires traffic to crisscross over to the left side of the roadway, separated by concrete barriers, between the proposed traffic signals located at the interchange ramps. This design eliminates several conflicting vehicle movements, particularly the left turns onto the ramps to US 129 Bypass, without the need for costly reconstruction of the existing bridge to provide the additional lanes that would be normally be necessary for other interchange designs.

Example DDI in Missouri

The Missouri Department of Transportation just opened a second DDI on July 12, 2010 and has received favorable public comments including the following:

"MoDOT gets a lot of complaints, but I wanted to say WELL DONE on the overpass project which officially opened on Monday, July 12th. The work the contractor(s) did by maintaining traffic flow had to be difficult at best, considering the amount of traffic in that area, but, the "traffic jams" were minimal at best. I go through that intersection 5-6 times at day, and welcome the new design, especially in the evenings, when the left turn lane always backs up. I was one of those that was against the new idea when it was first installed at I-44 & Kansas Expressway, but have become a convert and think ALL interchanges should be diverging diamonds. They are extremely efficient at cutting down on left turn crashes, and move a higher volume of traffic, in a shorter period. Again, thanks to MoDot and the contractors for a JOB WELL DONE!"

DDI under construction in Alcoa, TN. Designed by Gresham Smith and Partners