Leveraging Sidewalk Robots for Walkability-Related Analyses

Walkability is a key component of sustainable urban development, while collecting detailed data on its related features remains challenging due to the high costs and limited scalability of traditional methods. Sidewalk delivery robots, increasingly deployed in urban environments, offer a promising solution to these limitations. This paper explores how these robots can serve as mobile data collection platforms, capturing sidewalk-level features related to walkability in a scalable, automated, and real-time manner. A sensor-equipped robot was deployed on a sidewalk network at KTH in Stockholm, completing 101 trips covering 900 segments. From the collected data, different typologies of features are derived, including robot trip characteristics (e.g., speed, duration), sidewalk conditions (e.g., width, surface unevenness), and sidewalk utilization (e.g., pedestrian density). Their walkability-related implications were investigated with a series of analyses. The results demonstrate that pedestrian movement patterns are strongly influenced by sidewalk characteristics, with higher density, reduced width, and surface irregularity associated with slower and more variable trajectories. Notably, robot speed closely mirrors pedestrian behavior, highlighting its potential as a proxy for assessing pedestrian dynamics. The proposed framework enables continuous monitoring of sidewalk conditions and pedestrian behavior, contributing to the development of more walkable, inclusive, and responsive urban environments.

Robust Route Planning for Sidewalk Delivery Robots

Sidewalk delivery robots are a promising solution for urban freight distribution, reducing congestion compared to trucks and providing a safer, higher-capacity alternative to drones. However, unreliable travel times on sidewalks due to pedestrian density, obstacles, and varying infrastructure conditions can significantly affect their efficiency. This study addresses the robust route planning problem for sidewalk robots, explicitly accounting for travel time uncertainty due to varying sidewalk conditions. Optimization is integrated with simulation to reproduce the effect of obstacles and pedestrian flows and generate realistic travel times. The study investigates three different approaches to derive uncertainty sets, including budgeted, ellipsoidal, and support vector clustering (SVC)-based methods, along with a distributionally robust method to solve the shortest path (SP) problem. A realistic case study reproducing pedestrian patterns in Stockholm's city center is used to evaluate the efficiency of robust routing across various robot designs and environmental conditions. The results show that, when compared to a conventional SP, robust routing significantly enhances operational reliability under variable sidewalk conditions. The Ellipsoidal and DRSP approaches outperform the other methods, yielding the most efficient paths in terms of average and worst-case delay. Sensitivity analyses reveal that robust approaches consistently outperform the conventional SP, particularly for sidewalk delivery robots that are wider, slower, and have more conservative navigation behaviors. These benefits are even more pronounced in adverse weather conditions and high pedestrian congestion scenarios.

Model-based traffic state estimation for link traffic using moving cameras

Traffic State Estimation (TSE) is the process of inferring traffic conditions based on partially observed data using prior knowledge of traffic patterns. The type of input data used has a significant impact on the accuracy and methodology of TSE. Traditional TSE methods have relied on data from either stationary sensors like loop detectors or mobile sensors such as GPS-equipped floating cars. However, both approaches have their limitations. This paper proposes a method for estimating traffic states on a road link using vehicle trajectories obtained from cameras mounted on moving vehicles. It involves combining data from multiple moving cameras to construct time-space diagrams and using them to estimate parameters for the link's fundamental diagram (FD) and densities in unobserved regions of space-time. The Cell Transmission Model (CTM) is utilized in conjunction with a Genetic Algorithm (GA) to optimize the FD parameters and boundary conditions necessary for accurate estimation. To evaluate the effectiveness of the proposed methodology, simulated traffic data generated by the SUMO traffic simulator was employed incorporating 140 different space-time diagrams with varying lane density and speed. The evaluation of the simulated data demonstrates the effectiveness of the proposed approach, as it achieves a low root mean square error (RMSE) value of 0.0079 veh/m and is comparable to other CTM-based methods. In conclusion, the proposed TSE method opens new avenues for the estimation of traffic state using an innovative data collection method that uses vehicle trajectories collected from on-board cameras.