“…Moreover, he assumed that the distribution of desired velocitiesP 0 (v) depends on the density ρ and the average velocity V . Finally, he made several proposals for the velocity variance θ. Prigogine's model has been also improved by Andrews (1970aAndrews ( , b, 1973a, Phillips (1977Phillips ( , 1979a, PaveriFontana (1975), Nelson (1995) and others (Helbing, 1995c(Helbing, , d, 1996a(Helbing, , b, 1997a(Helbing, , d, 1998aWagner et al, 1996;Wagner, 1997aWagner, , b, c, 1998bNagatani, 1996aNagatani, , b, c, 1997aWegener and Klar, 1996;Klar et al, 1996;Wegener, 1997, 1999a, b;Shvetsov and Helbing, 1999). They modified the acceleration term, introduced velocity correlations among successive vehicles, investigated interactions among neighboring lanes, and/or considered space requirements.…”