“Ramp Metering: A Proven, Cost-Effective Operational Strategy—A Primer,” Federal Highway Administration
“Ramp Meters,” Wikipedia
“Cost Estimates for ITS Devices of the T-REX Project” Summary, US Dept. of Transportation, 11/2001
“The Minimum Yellow Timing for Ramp Meters,” Wang, Liu
“Case Studies of U.S. Freeway-to-Freeway Ramp and Mainline Metering and Suggested Policies for Washington State,” Jacobson, Landsman
“A Case for Freeway Mainline Metering,” Habobian
All you want to do is get on the freeway. Then a seemingly superfluous traffic signal stops you. Do ramp meters work?