Accessibility measures how well a location is connected to surrounding opportunities. We focus on accessibility provided by Public Transit (PT). There is an evident inequality in the distribution of accessibility between city centers or close to main transportation corridors and suburbs. In the latter, poor PT service leads to a chronic car-dependency. Demand-Responsive Transit (DRT) is better suited for low-density areas than conventional fixed-route PT. However, its potential to tackle accessibility inequality has not yet been exploited. On the contrary, planning DRT without care to inequality (as in the methods proposed so far) can further improve the accessibility gap in urban areas. To the best of our knowledge this paper is the first to propose a DRT planning strategy, which we call AccEq-DRT, aimed at reducing accessibility inequality, while ensuring overall efficiency. To this aim, we combine a graph representation of conventional PT and a Continuous Approximation (CA) model of DRT. The two are combined in the same multi-layer graph, on which we compute accessibility. We then devise a scoring function to estimate the need of each area for an improvement, appropriately weighting population density and accessibility. Finally, we provide a bilevel optimization method, where the upper level is a heuristic to allocate DRT buses, guided by the scoring function, and the lower level performs traffic assignment. Numerical results in a simplified model of Montreal show that inequality, measured with the Atkinson index, is reduced by up to 34\%. Keywords: DRT Public, Transportation, Accessibility, Continuous Approximation, Network Design

翻译：可达性衡量一个地点与周边机会的连通程度。本文聚焦于公共交通（PT）提供的可达性。研究表明，城市中心或主要交通走廊附近与郊区之间的可达性分布存在明显不平等。在郊区，糟糕的公交服务导致长期依赖私家车。需求响应式公交（DRT）比传统固定线路公交更适用于低密度区域。然而，其解决可达性不平等的潜力尚未被开发。相反，若不重视不平等性（如现有方法所示）地规划DRT，反而会加剧城市区域的可达性差距。据我们所知，本文首次提出一种名为AccEq-DRT的DRT规划策略，旨在减少可达性不平等的同时确保整体效率。为此，我们结合了传统公交的图表示与需求响应式公交的连续近似（CA）模型。两者被整合到同一多层图中，并基于该图计算可达性。随后，我们设计了一个评分函数来评估各区域对改善的需求，并适当加权人口密度与可达性。最后，我们提出一种双层优化方法：上层通过评分函数引导的启发式算法分配DRT车辆，下层执行交通流分配。在蒙特利尔简化模型上的数值结果表明，通过Atkinson指数衡量，不平等性降低了最多34%。关键词：需求响应式公交、公共交通、可达性、连续近似、网络设计