Development of proposed priority infrastructure for minibus-taxis and peak hour traffic count data

The paratransit industry in South Africa which mainly includes the minibus-taxis is growing at a fast pace. Thus, it has become the largest mobility supplier to the urban public. In Gauteng province, the economic hub of South Africa that includes Johannesburg, Tshwane and Ekurhuleni, minibus-taxis account for 46% of all peak-period passenger trips followed by private cars accounting for 44%, while buses and trains account for a combined total of 10% of peak-period. Unlike buses which have seen the provision of priority infrastructure at intersections in the form of bus rapid transit (BRT) with priority transit signals (PTS) to improve their efficiency, minibus-taxis currently do not enjoy the same benefits. However, any efforts of road authorities in South Africa to consider incorporating priority infrastructure for minibus-taxis would be constrained by the absence of literature suggesting the ideal choices and the design analytical procedures.
This research study aims to develop and evaluate design strategies for priority infrastructure for minibus-taxis at signalised intersections. Priority infrastructure at intersections can be in form of roadway facility infrastructure such as queue-jumping lanes, shared traffic lane, exclusive lanes or can be implemented via signal control. These infrastructure types are designed to provide efficiency benefits to road users mainly public transport such as buses. The first objective of this study is to develop an approach for identifying the design strategies for priority infrastructure for minibus-taxis at signalised intersections. A qualitative data method utilising document analysis technique is used to develop a framework matrix table to show the relationship between the geometric elements and the design treatments of priority infrastructure. Two categories of minibus-taxis (MBT) design strategies are then formed: 1) design strategies that only require repurposing of the existing intersection, 2) the design strategies that require major geometric improvements.
Secondly, an analytical approach is developed to evaluate the performance of two proposed design strategies using real world traffic data. To begin with, four isolated intersections in the city of Tshwane are evaluated for feasibility of the MBT design strategies. The framework matrix analysis developed earlier is utilised to select and evaluate the design strategies associated with the four intersections. In addition, the intersections are further assessed for safety, traffic operations and cost effectiveness. Eventually, the two most effective design strategies are selected for a detailed performance evaluation: 1) a shared MBT lane to be used by through movement minibus-taxis and left-turning vehicles (MBT+LT) and 2) a dedicated MBT lane for through minibus-taxis only. The approach uses modified analytical principles from the Highway Capacity Manual (HCM) to measure the performance of the selected design strategies using peak hour traffic data. The performance measures include volume to capacity ratio (v/c ratio), average vehicle delay, and adequacy of storage length of MBT priority lanes. The performances of existing intersections are compared with the performances of intersections after implementing the MBT design strategies. In general, the results show that the two proposed MBT design strategies significantly improved the performance of minibus-taxis at intersections while slightly reducing the performance of traffic in non-priority lanes.
Lastly, using the results from the two evaluated design strategies, a sensitivity analysis is performed on the modified HCM method to determine a range of traffic volumes for which the selected design strategies are feasible. Consequently, two models are set using a modified HCM method to evaluate two typical MBT design strategies involving a shared MBT lane and a dedicated MBT lane. The models are set to measure the v/c ratios of individual lanes on the approach as a measure of performances. The models are set to measure the highest v/c ratios while varying the traffic volumes at constant values of g/C ratios. The model outputs are in the form of graphs showing the relationship between left turning (LT) traffic, straight (MBT+T) traffic and v/c ratios at constant values of g/C ratios. These charts are developed as a planning and design guide when evaluating the feasibility of signalised intersections for the two evaluated MBT priority infrastructure types.
Overall, the study provides the first detailed results supporting the viability of priority infrastructure for minibus-taxis at signalised intersections. It also gives a detailed methodology and steps that could be used by traffic engineers and planners to design and evaluate the performance of priority infrastructure for minibus-taxis at signalised intersections. The matrix framework method and graphs for traffic volumes could provide planners with a structured way to identify feasible designs for the priority infrastructure for minibus-taxis at signalised intersections. The methodology used in this study can be adopted to evaluate other types of design strategies not evaluated in this study.
The study concludes that with well optimised design solutions, it is possible to use priority infrastructure to improve the performance of minibus-taxis at signalised intersections without adversely affecting the performance of traffic in the non-priority lanes.

南非的准公共交通行业，主要包括微型巴士出租车，正以迅猛的速度发展。因此，它已成为城市公共交通最大的流动性供应商。在南非的经济中心——豪登省，包括约翰内斯堡、茨瓦内和埃库胡伦尼，微型巴士出租车占所有高峰时段旅客出行方式的46%，其次是私人汽车，占比44%，而公交车和火车合计仅占高峰时段的10%。与享有在交叉口优先基础设施（如快速公交系统（BRT）和优先通行信号（PTS）以改善其效率的交叉口优先权）的公交车不同，微型巴士出租车目前并未享受到同样的待遇。然而，南非道路当局在考虑为微型巴士出租车整合优先基础设施的任何努力都将受到缺乏关于理想选择和设计分析程序的文献支持的制约。本研究旨在开发并评估在信号交叉口为微型巴士出租车提供优先基础设施的设计策略。交叉口优先基础设施可以采取道路设施基础设施的形式，如跳排队车道、共享车道、专用车道，或通过信号控制实施。这些基础设施类型旨在为道路使用者，尤其是公共交通（如公交车）提供效率效益。本研究的第一项目标是开发一种识别信号交叉口微型巴士出租车优先基础设施设计策略的方法。采用文献分析法这一定性数据方法，构建了一个框架矩阵表，以展示几何要素与优先基础设施设计处理之间的关系。随后形成了两类微型巴士出租车（MBT）设计策略：1）仅需要重新利用现有交叉口的策略，2）需要重大几何改进的策略。其次，开发了一种分析方法，以利用真实世界交通数据评估两种提议的设计策略的性能。首先，对茨瓦内市内的四个孤立交叉口进行评估，以确定MBT设计策略的可行性。利用先前开发的框架矩阵分析来选择和评估与四个交叉口相关的设计策略。此外，对交叉口进行进一步评估，包括安全性、交通运营和成本效益。最终，选择了两种最有效的设计策略进行详细性能评估：1）供直行微型巴士出租车和左转车辆（MBT+LT）通行的共享MBT车道，2）仅供直行微型巴士出租车通行的专用MBT车道。该方法使用修改后的《公路容量手册》（HCM）的分析原则，利用高峰时段交通数据来衡量所选设计策略的性能。性能指标包括流量与容量比（v/c比）、平均车辆延误和MBT优先车道存储长度的充足性。将现有交叉口的性能与实施MBT设计策略后的交叉口的性能进行比较。总体而言，结果显示，两种提议的MBT设计策略显著提高了微型巴士出租车在交叉口的性能，同时略微降低了非优先车道交通的性能。最后，利用两种评估的设计策略的结果，对修改后的HCM方法进行了敏感性分析，以确定所选设计策略可行的交通量范围。因此，使用修改后的HCM方法设置了两个模型，以评估涉及共享MBT车道和专用MBT车道的典型MBT设计策略。这些模型旨在测量接近道路的单个车道的v/c比，作为性能的衡量指标。这些模型在保持g/C比恒定值的同时，变化交通量。模型输出以图表的形式呈现，显示了左转（LT）交通、直行（MBT+T）交通和v/c比之间的关系。这些图表作为评估信号交叉口两种评估的MBT优先基础设施类型的可行性时的规划与设计指南。总体而言，本研究提供了首个支持在信号交叉口为微型巴士出租车提供优先基础设施可行性的详细结果。它还提供了详细的方法和步骤，供交通工程师和规划者使用，以设计和评估信号交叉口微型巴士出租车优先基础设施的性能。矩阵框架方法和交通量图表可以为规划者提供识别信号交叉口微型巴士出租车优先基础设施可行设计的结构化方法。本研究中使用的方法可以用于评估本研究未评估的其他类型的设计策略。研究结论表明，通过优化设计解决方案，可以使用优先基础设施在不损害非优先车道交通性能的情况下，提高微型巴士出租车在信号交叉口的表现。