TY  - JOUR
PY  - 2015//
TI  - Parametric modeling of the heteroscedastic traffic speed variance from loop detector data
JO  - Journal of advanced transportation
A1  - Wang, Haizhong
A1  - Li, Zhixia
A1  - Hurwitz, David
A1  - Shi, Jianjun
SP  - 279
EP  - 296
VL  - 49
IS  - 2
N2  - Traffic speed variance is defined as a measure of the dispersion of space mean speeds among drivers. Empirical speed-density observations exhibit a structured traffic speed variance, which has been found to be associated to the roadway crash rate, the fatality rate, and travel time variability. The objective of this paper is to propose a generalized traffic speed variance function to describe this structured variance. The proposed speed variance function is a response of the speed-density curve with two additional parameters. The estimation of the model parameters in the proposed traffic speed variance function can be carried out through an iterative nonlinear least-square algorithm (i.e., LevenbergMarquardt). A series of logistic speed-density curve with varying parameters are used in the proposed traffic speed variance function with different levels of performance. The proposed traffic speed variance model can potentially help to unveil the underlying mechanism of empirical traffic phenomenon such as spontaneous congestion or capacity reduction. Copyright © 2013 John Wiley & Sons, Ltd.<p />  <p>Language: en</p>
LA  - en
SN  - 0197-6729
UR  - http://dx.doi.org/10.1002/atr.1258
ID  - ref1
ER  -