Florida takes French lessons in interchange design
The Florida Department of Transportation (FDOT) is taking a French lesson in designing interchanges by recommending Sarasota County implement an X-shaped design to move traffic safely through a high-volume intersection.
The FDOT submitted a Project Development Summary Report to the Federal Highway Administration (FHWA) recommending a diverging diamond interchange (DDI) at the intersection of University Parkway and I-75 that briefly directs drivers to the left side of the road. The DDI, first developed in France, reduces a vehicle’s possible points of conflict when making left turns by eliminating the need to cross oncoming traffic to make the turn.
The X-shaped design requires fewer traffic signals and allows high volumes of traffic to move quickly through the interchange. DDIs also increase turning capacity on and off interstate ramps and eliminate wrong-way entry onto ramps.
The DDI design first entered the United States in Springfield, Missouri, where the new intersection reduced traffic delays by up to 60 percent and increased throughput by 10 to 30 percent, according to the FHWA. The Missouri DDI reduced the number of conflict points from the usual 26 points to a low 14 points, improving safety and efficiency. The FDOT worked closely with the Missouri Department of Transportation (MoDOT) in its design.
The cost of the entire project is estimated around $1.24 billion for which there is currently no funding.
Maryland, Georgia, Tennessee, Utah, Oregon, New York and several other states are either in the process or considering converting high-volume interchanges in their states to diverging diamond designs. A video of how the DDI design works can be viewed on the web at www.i-75pde.com/sarasota/diamond.html.
– Allison Cook
America’s most dangerous highway
A movie about one man’s struggle with ending it all, “Leaving Las Vegas,” could just as easily have described the trip along Interstate 15.
The 181-mile stretch between Clark County, Nevada and San Bernardino County, California has more fatalities than anywhere else in the country. According to a federal study of traffic accident deaths from 1994 to 2008, 1,069 people were killed in 834 fatal accidents on the speed-stoked, open-country stretch of freeway.
The Las Vegas Convention and Visitors Authority estimates some eight million drivers make their way to Las Vegas from southern California each year. EW
Word for word
“Instead of a shining American symbol of resilience and strength, we have a hole in the ground. Rebuilding the towers and ground zero is a moral imperative. Putting 10,000 people to work in the middle of a severe recession is an economic imperative.”
– U.S. Rep. Carolyn Maloney, to protesting construction workers at the World Trade Center site urging a quick rebuilding process amidst project delays.
“The economic state of the country is the only thing that is deterring people from doing anything right now. When the economy picks up, we’ll start getting more bites.”
– Developer Al Schoeneman, to the Argus Leader (Sioux Falls, South Dakota) about using a wait-and-see approach on new projects.
“If that $1 million in SDC forgiveness wasn’t there, this project would stop and not move forward. Without the waivers, this project simply would not pencil out.”
– Developer Karl Ivanov of I&E Construction, to The Oregonian (Portland), about his retail development in the town of Molalla, which has made the unusual move of waiving up to $1 million in building fees through 2010.
– Mike Anderson