文献翻译

北京邮电大学世纪学院毕业设计（论文）文献翻译题目牛街主干道连续交通计算机仿真学生姓名余楠学号 07030135 专业名称计算机科学与技术年级 2007级指导教师职称所在系（院）计算机科学与技术2011年 3月 14日Micro-simulated Comparisons of Alternative SignalizedPedestrian CrossingsABSTRACTFour different signalized pedestrian crossing technologies are analyzed using the VISSIM micro-simulation tool. The objective is to study how changing the crossing type affects various measures of effectiveness for both vehicles and pedestrians. A simple network with a single junction is coded with two different pedestrian compliance levels. Two different approaches are taken for simulating pedestrian behavior in VISSIM, with and without interactions between pedestrians. In addition, various methods are included for modeling pedestrian compliance with signal instructions, by assuming in one case that 80% of pedestrians continue to cross for a limited time after a red signal is shown. Data is generated for travel times, travel distances, delay and the number of stops. Results are presented with a discussion on the suitability of the various pedestrian crossing approaches, based on the measures of effectiveness calculated from the simulations.INTRODUCTIONSolutions that enable pedestrians to safely cross at junctions have long sought to balance the need for maintaining traffic flows while protecting the pedestrian. Normally, the delay that pedestrians face is not considered in the selection of crossing technologies. Finding ways to reduce pedestrian delay and to make environments safer for pedestrians are seen as a means to encourage increased walk ability in cities.This paper seeks to examine a variety of signalized pedestrian crossing technologies and examine various measures of effectiveness primarily from the perspective of the pedestrian. Specifically, the average delay and total travel time, and the mean number of stops facing pedestrians are examined. Similar measures are also calculated for cars. Four different types of pedestrian crossing technologies are examined and compared: scrambled, staggered, crossing with exclusive (but notscrambled) pedestrian phase and crossing with the pedestrian phase parallel to the vehicle phase.The VISSIM micro-simulation package is used for this analysis and the impact of different assumptions on pedestrian behavior are analyzed. Specifically, we simulate scenarios where VISSIM allows for no interactions between pedestrians and compare these to scenarios with interactions between pedestrians (following the logic of the car-following model). We also make various assumptions on the level of compliance with signal instructions on the part of pedestrians and further compare the results across both signal technologies and simulation scenario.The next section reviews the various signal technologies that are analyzed and identifies previous work in this area. We then explain the simulation method used and the detailed assumptions used in our scenarios. This is followed by a discussion of results and conclusions.PEDESTRIAN CROSSING AND SIGNAL TECHNOLOGIES Scrambled crossings have not been widely adopted. One of the main concerns regarding their use is that they are difficult to synchronize with adjacent signals in a coordination plan and will increase vehicle and pedestrian delay as long signal cycles are required. However, Abrams and Smith, analyzing a hypothetical junction with Scrambled and parallel pedestrian phasing, found that vehicular delay in through lanes increased and pedestrian delay increased to over 200% for Scrambled phase crossings compared to Parallel pedestrian phase crossings .The most important benefit of scrambled crossings and crossings with an exclusive pedestrian phase is that they provide a safety benefit as all conflicts between vehicular movements and pedestrians are eliminated. Locations with a separate pedestrian phase are found to be associated with lower pedestrian accidents for intersections with moderate to high pedestrian volumes when compared with both standard signalized intersections and intersections that have no pedestrian signals . The safety benefit from eliminating conflicts between pedestrians and vehicles hasbeen estimated to reduce crashes in the range of 7% to 63% and by 66% in another study over a ten year period.Improving pedestrian safety by elimination of conflicts, however, comes at the cost of degradation of traffic flow conditions . Moreover, pedestrian compliance levels play an important role in assessing the success or otherwise of the Scrambled crossings as in one study they proved to be very safety-beneficial in a small town, while in a large town they did not prove effective because of very low pedestrian compliance levels . Another study has demonstrated a significant decrease in the rate of pedestrian-vehicle conflicts at a target intersection after the pedestrian-scramble phasing was implemented. However the findings also demonstrated an increase in the number of pedestrian violations after implementation of the scramble .The safety argument has also been challenged on the grounds that various crossing types had little effect, if any, on the number of pedestrian accidents, and no effect on the number of vehicle collisions. At locations with low vehicle volumes, scramble phasing made little difference in pedestrian safety as pedestrian compliance decreased significantly with low traffic volumes.The low traffic volume is precisely the condition where Scrambled crossing types are normally considered. Scrambled junctions also result in long signal cycle lengths during the exclusive pedestrian phase and the extra pedestrian clearance time needed for diagonal crossings. Long signal cycles are associated with high driver non-compliance which might decrease the safety benefit arising from the separation of pedestrian and vehicle movements. The delay experienced by pedestrians increases with the introduction of Scrambled crossings but the distance traveled decreases and this decrease has been estimated to be 5% to 7% and in another case 13% .Staggered pedestrian crossings give a clear reduction in vehicular delay in comparison to pedestrian crossings with an exclusive pedestrian phase, however, the benefits to pedestrians are less clear. For example delay to pedestrians increases due to the increase in travel distance with staggered crossings.Other types of pedestrian crossings, which are not at a traffic junction, are also commonly used. These include various types of mid-block pedestrian crossings inuse in different parts of the world. In British practice, there are two types of such crossings; controlled and uncontrolled. Controlled crossings are Pelican crossings, where pedestrians have to register there intention to cross using a push button to activate a signal, and Puffin crossings which are similar to Pelican crossings but employ pedestrian detectors. Also there are variants such as Toucan crossings, which are used for pedestrians and cyclists and Equestrian crossings. Uncontrolled crossings are known as Zebra crossings which give precedence to pedestrians to cross the road over vehicular traffic. Mid-block and uncontrolled pedestrian crossings are not analyzed in this paper and are not discussed further.信号灯控制行人过人行道的替代微观比较摘要四种不同的信号化的人行横道技术利用VISSIM的微观模拟工具进行了分析。