Research On Signal Timing Parameters And Optimization Methods Of Mixed Traffic Flow

This dissertation chooses the key problem in urban traffic signal control—signal timing parameters and optimization methods—as its research target. This dissertation is consisted of introduction, measurement of vehicle conversion factor, measurement on the spot of saturation flow rate, optimization methods of signal timing parameters of mixed traffic, and conclusion and expectation. The contents are as follows. (1) The introduction introduces the background, actuality, meaning and main contents of this dissertation (2) Measurement of motor vehicle conversion factor. T The selection of standard vehicle is the precondition and basis for motor vehicle conversion factor analysis. Since cars maintain much large proportion in cities of China, the dissertation selects car as standard vehicle. The selection fits the criterion commonly domestically and internationally. Headway serves as the measurement of criterion for vehicle conversion factor in the paper. The reasons are as follows: ①Vehicle conversion factor is defined as the equivalent that non-standard vehicles contrast with standard vehicles in terms of spatio-temporal. When it comes to capacity analysis, conversion factor is used as equivalent that non-standard vehicles contrast with standard vehicles in terms of time. ②When non-standard vehicles are in the mixed traffic flow, it makes different effects on traffic flow in a free way of driving,velocity and delay, etc, contrast with standard vehicle. The impact is reflected from the headways when the drivers choose different following distance. So headway is the overall presentation of various vehicle types resulting in impact on traffic flow in all aspects. ③The factor resulting in impact on headway is composed of two parts, namely the gap between the rear of the front vehicle and the head of the following vehicle and the vehicle length. When other factors remain unchanged, the longer the vehicle length is, the longer the time that the vehicle holds actuated loop detectors is, accordingly, the longer headway is , and vice versa. So, headway is relative to vehicle length. ④In traffic control system,vehicle length and headway are the basic information that can be obtained by loop detectors, so if conversion factor measurement models are established in accordance with the data of vehicle length and headway, the models will be easily used in traffic control systems. ⑥Headway is the most evident parameter in traffic flow directly obtained from traffic survey. It is comparatively precise in computation without accumulative error. The difference of vehicle headways can be indicated only in case of saturation. Therefore, the traffic situation studied in the paper is of saturation state. The paper selects headway under saturation conditions as datum value. The vehicle conversion factor measurement method is established by studying the impact of standard and non-standard vehicles on the headways of standard vehicles. The vehicle conversion factor dealing with different vehicle length is calibrated by studying the impact of non-standard vehicles with various lengths on the headways of standard vehicles. Through traffic survey on nineteen lanes from nine inlets of six typical intersections in Changchun City during peak periods, vehicle conversion factor in accordance with the vehicle length is certain. (3) Measurement of bicycle conversion factor. Since mutual the influence of bicycle and motor vehicle is embodied in intersection with two phases, so bicycle (right bicycle and turn bicycle) conversion factors are studied bases on intersection with two phases. Measurement of right bicycle conversion factor. In the intersection with two phases, the traveling lines of right bicycles and right vehicles are parallel. Though right bicycles and right vehicles affect reciprocally, comprehensive flow of the right bicycles and the straight vehicles is a fixed value when there is no effect ofbicycles and vehicles traveling in other directions. Based on which, the measurement model of right bicycle is established. Through traffic survey on four typical intersections in Tianjin City, the straight bicycle conversion factor is 0.275. Measurement of left turn bicycle. Fist the delay time of one left turn bicycle affecting on right vehicle is determined. Then the number of right vehicle traveling in this delay time that is left turn bicycle conversion factor is calculated. Last through traffic survey on three typical intersections in Tianjin City and Shenyang City, the left turn bicycle conversion factor is 0.33. (4) Study on measurement on the spot of vehicle saturation flow rate. For saturation flow rate is different with the difference of geometric condition, channelization model and traffic conflict of different traffic flow intersection etc, which is so complex, it is suggested that data on the spot of saturation flow rate be used. Based on definition of vehicle saturation flow rate and data that can be obtained through traffic survey, the measurement model and measurement method are given. Traffic survey has bee carried out on six typical intersections in Changchun city and the outcome is given. Study on measurement on the spot of bicycle saturation flow rate. Because discharging characteristic of bicycle is different from that of vehicle. The definition of bicycle saturation flow rate is given. And bicycle saturation flow rate is calibrated by traffic survey data. Accordingly, the outcome is given. Based on definition of bicycle saturation flow rate and data that can be obtained through traffic survey, the measurement model and measurement method are given. Traffic survey has bee carried out on four inlets of two typical intersections in Tianjin city and the outcome is given. (6) Study on the optimization methods of signal timing parameters of mixed traffic. This chapter contains the optimization methods of cycle length and split of typical intersections with two phases and four phases in mixed traffic situation. In the traditional signal timing methods, signal timing is designed at intersections with bicycle traffic subordinate to motorized vehicle traffic. Even if signal lamp is installed for bicycle traffic, the signal timing parameters of bicycle are obeyed with motorized traffic in the same phase in which vehicle-bicycleconflict is not considered The condition of mixed traffic is taken into account in this dissertation from beginning to end. Status of bicycle traffic is parallel with that of motorized traffic. For the optimization methods of cycle length, In this chapter, the general optimization methods of cycle length are discussed in detail, including TRRL method, ARRB method, HCM method and conflict point method. The defects of these methods are analyzed by comparison. TRRL method and ARRB method are not applicable when density is high and traffic volume is low and when degree of saturation is approximatively 1.0. HCM method is essentially formula of minimum cycle and don't fit with real-time adaptive traffic control system. Conflict point method doesn't The traffic intension model is established in the light of two traffic flow parameters: traffic volume and time occupancy. Conflict point method isn't applicable in intersection with four phases in which change interval is made, the formula is so complex that many parameters is hardly obtained and the method is not practical. The traffic intension model that is established in the light of traffic volume and time occupancy is explained in detail. Therefore, traffic load at the intersection can be reflected by the calibration of these two traffic flow parameters as the gist of cycle length optimization. The traffic intension model can reflect traffic situation in which density is high and traffic volume is low Parameters in this method can be easily detected and different optimization objects can be realized in peak periods and low periods. Optimization methods of cycle length studied in this chapter are based on the optimization method of cycle length according to the traffic intension model According to bicycle conversion factor and the optimization methods of cycle length in vehicle traffic flow, new optimization methods of cycle length are presented with regard to typical intersections under the mixed traffic situation. For the optimization methods of split, a retrospect is first made on "equivalent saturation"put forward by Webster Secondly a study is on the confirming method of the critical phases about overlapping phase and non-overlapping phase. Then effect green Time of traffic flow of each phase is determined with the principal of "equivalent saturation". Afterwards the calculation of actual green time is given. At last the difference in...