The conventional approach to congestion-related problems, which involves increasing the capacity of an intersection simply by adding lanes, has unfortunately seen diminishing returns. What alternative intersection treatments and reconstruction methods are available to solve such capacity-related problems? Developed by Dr. Rossow, this course discusses conventional intersection treatments and the issues associated with them, and then moves on compare and contrast jughandles and other alternative intersection treatments available to solve congestion-related problems. This course will start off by assessing conventional intersection treatments in terms of their long-term performance and issues with diminishing returns. For example, if the addition of a 2nd through-lane adds 15 years to the life of the intersection before it reaches capacity, the addition of a 3rd through-lane adds only 10 years, and a 4th through-lane adds only 6 years. Furthermore, large intersections increase loss time due to longer clearance intervals, protected left turn phasing, longer pedestrian clearance times, greater imbalances in lane utilization, and potential queue blockages caused by the resulting longer cycle lengths. Alternative intersection treatments/reconstruction methods for signalized intersections will then be presented in 3 categories:

1. Intersection reconfiguration
2. At-grade indirect movements
3. Grade separation

Many of these alternative intersection treatments are commonplace, while others have seen limited or regional use. But the common element in each of these alternative intersection treatments is the reduction in conflict points at the intersection, providing safety and operational benefits by reducing the number of phases and conflicting volumes at a single location. This online traffic engineering PDH course is based on Ch. 10 of Report No. FHWA-HRT-04-091 “Signalized Intersections: Informational Guide,” written by Lee A. Rodegerdts, et. al., August, 2004, and sponsored by the Federal Highway Administration under Contract No. DTFH61-98-C-00075, Task Order No. B98C75-009.

Learning Objectives

At the successful conclusion of this course, you’ll be able to identify and discuss:

• Reconfiguration: removal of intersection skew angle
• Reconfiguration: removal of deflection in travel path for through vehicles
• Reconfiguration: conversion of four-leg intersection to two T-intersections
• Reconfiguration: conversion of two T-intersections to four-leg intersection
• Reconfiguration: closure of intersection leg
• Indirect left turn treatment: jughandle
• Indirect left turn treatment: median U-turn crossover
• Indirect left turn treatment: continuous flow intersection
• Indirect left turn treatment: quadrant roadway intersection
• Indirect left turn treatment: super-street median crossover
• Grade separation treatment: split intersection
• Grade separation treatment: diamond interchange