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在传统的交通流理论中,通常用确定性函数来描述交通流的速度-密度关系。但实际上,交通流存在着相当大的随机性和波动性:在一定局部密度的情况下,往往存在多种短时局部速度。为了能更加真实地描述速度和间距之间的关系,对NGSIM数据进行了研究和统计,对不同车头间距情况下的交通流速度分布建模。结果表明:当交通流密度较小时,速度分布大致服从对数正态函数;而当交通流密度较大时,交通处于阻塞状态,速度分布则更接近于负指数函数。
In traditional traffic flow theory, the deterministic function is usually used to describe the speed-density relationship of traffic flow. However, in fact, there is a considerable randomness and volatility of traffic flow: in the case of a certain local density, there are often a variety of short-term local speed. In order to describe the relationship between velocity and spacing more faithfully, the NGSIM data are studied and statistically analyzed. The velocity distribution of traffic flow is modeled under different head spacings. The results show that when the traffic flow density is small, the velocity distribution generally obeys the logarithm normal function; while when the traffic flow density is large, the traffic is in a blockage state and the velocity distribution is closer to the negative exponential function.