viernes, 24 de septiembre de 2010

Alternative Intersection and Interchange Designs

Today's transportation professionals, with the limited resources available to them, are challenged to meet the mobility needs of an increasing population. At many highway junctions, congestion continues to worsen, and drivers, pedestrians and bicyclists experience increasing delays and heightened exposure to risk. Today's traffic volumes and travel demands often lead to safety problems that are too complex for conventional intersection designs to properly handle. Consequently, more engineers are considering various innovative treatments as they seek solutions to these complex problems.

The Alternative Intersections/Interchanges: Informational Report covers four intersection and two interchange designs that offer substantial advantages over conventional at-grade intersections and grade-separated diamond interchanges. It also provides information on each alternative treatment covering salient geometric design features, operational and safety issues, access management, costs, construction sequencing, environmental benefits and applicability. The four alternative intersection treatments covered in this report are displaced left-turn (DLT), restricted crossing U-turn (RCUT), median U-turn (MUT) and quadrant roadway (QR) intersections. In addition the two alternative interchange designs include double crossover diamond (DCD) and DLT interchanges. The report and corresponding Tech Briefs can be found on the Web as follows:

Alternative Intersections/Interchanges: Informational Report (AIIR)

Double Crossover Diamond Interchange (Tech Brief)

Displaced Left-Turn Intersection (Tech Brief)

Displaced Left-Turn Interchange (Tech Brief)

Median U-Turn Intersection (Tech Brief)

Quadrant Roadway Intersection (Tech Brief)

Restricted Crossing U-Turn Intersection (Tech Brief)


This article is extracted from ITE newsletter and ITE thank to
Mr. Lincoln Cobb and Mr. Ed Stollof for contributing these references.


FHWA Roundabouts and Mini Roundabouts Technical Summaries

This technical summary is designed as a reference for State and local transportation officials, Federal Highway Administration (FHWA) Division Safety Engineers, and other professionals involved in the design, selection, and implementation of roundabouts. Its purpose is to provide an overview of safety considerations in the design, implementation, and operation of roundabout intersections in urban, suburban, and rural environments where design considerations can vary as a function of land uses, travel speeds, volumes of traffic by mode (e.g., car, pedestrian, or bicycle), and many other variables.

This technical summary explores the characteristics of modern roundabouts while reinforcing the need to apply a principles-based approach to design. It provides readers with an overview of the key considerations for planning, analysis, and design of single-lane and multilane roundabouts. Section 1 of this document summarizes the characteristics of roundabouts. Section 2 presents benefits of roundabout intersections compared to traditional signalized and/or stop-controlled intersections. Sections 3-6 provide an overview of user, location, operational and design considerations respectively.

The information presented in this summary outlines the principles described in the FHWA document Roundabouts: An Informational Guide and the forthcoming 2nd Edition of that document (hereafter referred to as the Roundabout Guide), which is in progress at the time of this writing and due to be published in 2010. Specific considerations for mini-roundabouts are summarized in a separate FHWA document titled Mini- Roundabouts Technical Summary.

Please clic en the next link to see the information:

Roundabouts

http://safety.fhwa.dot.gov/intersection/roundabouts/fhwasa10006/

Mini- Roundabouts

http://safety.fhwa.dot.gov/intersection/roundabouts/fhwasa10007/

Regards

Gregorio