Browsing by Author "Wang, Kai"

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    Evaluating the Effectiveness of State Toward Zero Deaths Programs
    (Center for Excellence in Rural Safety, 2012-11) Munnich, Lee W. Jr.; Douma, Frank; Qin, Xiao; Thorpe, J. David; Wang, Kai
    Since 2001 approximately 30 U.S. states have adopted programs to reduce traffic fatalities to zero with names such as Vision Zero, Target Zero, or Toward Zero Deaths (TZD). TZD is now being promoted as a national strategy by a coalition of transportation and safety groups. Successful TZD programs have five characteristics: 1) an ambitious goal of eliminating traffic fatalities and serious injuries; 2) high levels of inter-agency cooperation in pursuit of the TZD goal among state departments of transportation, public safety, health, and other relevant agencies; 3) a comprehensive strategy addressing all 4 E’s – engineering, enforcement, education, and EMS elements of traffic safety; 4) a performance-based, data-driven system of targeting resources and strategies where they will have the greatest impact in reducing traffic fatalities; and 5) policy leadership from relevant entities, including the Governor, the state legislature, and the heads of state agencies. While many of the state TZD programs are relatively new and emerging, four state programs have been around long enough to have enough years of crash data to evaluate the impacts of the programs – Minnesota, Idaho, Utah and Washington. Statistical tests on these four programs support the conclusion that implementing TZD programs accelerates the reduction of fatality rates. The acceleration rate varies from state to state, taking time for a new program to gain its full effect. Although each state has different degrees of temporal effect of its TZD program, the average effect is more and more apparent over time.
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    Towards a Metropolitan Fundamental Diagram using Travel Survey Data
    (PLoS One, 2016) Wang, Kai; Levinson, David M
    Using travel diary data from 2000-2001 and 2010-12 this research examines fundamental traffic relationships at the metropolitan level. The results of this paper can help to explain the causes of some traffic phenomena. First, trip numbers on the network in the Minneapolis - St. Paul, Minnesota (Twin Cities) region show a bimodal diurnal pattern, with more trips in the afternoon. This relationship holds for full-time work and for non-work trips, but not part-time work trips. Second, network average speed by time of day can be explained by trip length and cumulative number of vehicles on the road. A clockwise hysteresis loop is found in the Metropolitan Fundamental Diagram in the morning period and a reverse process happens in the afternoon.