PATH

Intelligent Transportation Systems (ITS), ushered in by ISTEA in 1991 and advanced under TEA-21 in 1998, fundamentally alter transportation planning and implementation in the United States. ITS shifts emphasis away from new construction and capacity to more efficient management of existing systems, in the process requiring increased coordination and integration of standards, systems, and policies. The National ITS Architecture provides a framework for integration, but leaves the majority of the implementation decisions to the state, regional, and local levels. California is well-positioned...

Cooperative Adaptive Cruise Control (CACC) provides an intermediate step toward a longer-term vision of trucks operating in closely-coupled automated platoons on both long-haul and short-haul freight corridors. There are important distinctions between CACC and automated truck platooning. First, with CACC, only truck speed control will be automated, using V2V communication to supplement forward sensors. The drivers will still be responsible for actively steering the vehicle, lane keeping, and monitoring roadway and traffic conditions. Second, while truck platooning systems have relied on a...

Understanding the benefits of improved traffic flow (reduced congestion) is critical to the assessment of investments in infrastructure or traffic management and control. Improved flow should lead to reductions in travel time, vehicle emissions, fuel usage, psychological stress on drivers, and improved safety. However, the manner in which safety is improved by smoothing traffic flow is not well understood. The documented research is aimed at shedding light on the complex relationships between traffic flow and traffic accidents (crashes).

The Carquinez Bridge ETC project is a pilot project of a statewide toll bridge improvement project undertaken by Caltrans. Caltrans owns and operates nine toll bridges statewide. Over the last five years, traffic on all area bridges has increased from 129 million vehicle crossings in Fiscal year (FY) 1992-93 to 140 million in FY 1996-97, with an average annual rate of 2 percent as indicated in Figure 1. However, the toll facilities are antiquated. The bridges use a toll collection system known as Toll Registration, Audit and Collection (TRAC) installed in the early 1980s, and tolls have...