IP multicast is an efficient point-to-multipoint distribution mechanism. However, there are a number of scenarios in which a reverse, multipoint-to-point aggregation mechanism is highly desirable. We introduce a programmable mechanism, called gathercast, to support the aggregation of packets without altering any of the routing or forwarding mechanisms of the Internet. Gathercast is based on act...

BY XIAOYUE CATHY LIU, E.I.T., YINHAI WANG, PH.D., BASTIAN J. SCHROEDER, PH.D., AND NAGUI M. ROUPHAIL, PH.D. Introduction According to the 2011 Urban Mobility Report,1 roadway congestion cost a total of $101 billion and induced a total delay of 4.8 billion hours in the United States in 2010, with approximately 60 percent of the congestion occurring on freeways. Strategies have been implemented t...

INTRODUCTION TSIS/CORSIM and WATSim are microscopic, integrated, simulation models. INTEGRATION, on the other hand, models only the aggregate speed-volume interactions of traffic and not the details of a vehicle's lane-changing and car-following behavior; thus, it is commonly classified as a mesoscopic integrated simulation model. INTEGRATION is a routing-oriented model for mixed networks (1,2)...

Urban sprawl often has a negative connotation, used as a derogatory label for certain forms and consequences of land development that are seen as environmentally and socially unpleasant. Although sprawl may be seen as offensive, there may be other, far greater and more harmful consequences of sprawl. The literature indicates that rates of negative health outcomes, such as obesity, tend to be hi...

With little investment required for operating in streets, bus services are often designed to serve many overlapping routes with frequent stops. To upgrade services and attract choice riders, major bus routes should be provided with exclusive lanes, preferential signals, and fewer but more distinct stops. The Federal Transit Administration’s (FTA) Bus Rapid Transit (BRT) program is aimed at upgr...

Studies that develop estimates of the value of travel time savings (VTTS) for car travel typically assume that the VTTS of the driver is the only relevant measure of the worth of time savings. Although there is a recogntion that the presence of passenger’s may condition the driver’s choice of route and VTTS, the evidence is somewhat limited on the impact that the number of passengers has on the...