In order to evaluate the service level of roundaboutsintuitively, a new delay model of signalized roundabouts isestablished. According to traffic flow characteristics in thesignalized roundabout, vehicle delays on roundabouts aredivided into two parts： entrance delay and circulating lanedelay. Entrance delay is calculated by the delay model inHCM2010. Circulating lane delay is studied by analyzingconflict behavior in signalized roundabouts, and the delaymodels of traffic flows turning in different directions areestablished based on the motorcade analysis method. Finally,the simulation software Vissim, calibrated with field data, isused to verify the model. The simulation results show that theaverage relative error of the model is 10. 1%, meeting theaccuracy requirements. Therefore, the delay model properlyreflects the operation efficiency of a roundabout, and can thusorovide a scientific basis for the design of control schemes.
Liu HuanfengSong XianminZhang LibinTao PengfeiYang Qiujie
The effects of the interactions between bi-directional pedestrians on the crossing time and the crosswalk width are studied. Firstly,the crossing process of bi-directional pedestrians is analyzed.The total crosswalk time is divided into a discharge time and a crossing time. The interactions between bi-directional pedestrians are quantified with the drag force theory. Then,a model is developed to study the crossing time based on the kinetic energy theory and momentum theory. Subsequently,the related parameters of the proposed model are calibrated with observed information. The relationships among crosswalk width,signal time,pedestrian volume and level of service are simulated with the proposed model. The results are verified and compared with other models. The proposed model has an absolute value of relative error of 9. 38%,which is smaller than that of the Alhajyaseen model( 15. 26%) and Highway Capacity Manual( HCM) model( 12. 42%). Finally,suggested crosswalk widths at different conditions are successfully estimated with the proposed crossing time model.
Ningbo CaoYongheng ChenZhaowei QuLiying ZhaoYanfei LiQiujie Yang
The phenomenon that pedestrians do not walk in the crosswalk during pedestrian green is defined as overflow violation, which is illegal but common. Broadly varying crossing positions at far-side cross-section may result in widely distributed conflict points with left-turning and right-turning vehicles, which may cause the occurrence of severe conflicts. This paper proposes a model to estimate the overflow pedestrians' crossing positions at the far-side cross-section of signalized crosswalk, which enables us to better understand pedestrian overflow violation behavior and finally facilitate their safety. After analysis, the intersection geometry and destination are determined as the critical factors causing pedestrians to overflow. And then, Weibull distribution is employed to describe the stochastic characteristics of overflow pedestrians' crossing position distribution at the far-side cross-section. A crossing position distribution model which takes the crosswalk length, width and distance between crosswalk and destination into account is developed. The established model is validated by comparing the observed pedestrian crossing positions with the estimated crossing positions. The validation results suggest that the established model is capable of being adopted to estimate the overflow pedestrians' crossing positions at far-side cross-section. Based on the model, countermeasure for overflow violation can be put forward to prevent pedestrians from walking outside the crosswalk.
