A Tale of Many Cities: Universal Patterns in Human Urban Mobility

The advent of geographic online social networks such as Foursquare, where users voluntarily signal their current location, opens the door to powerful studies on human movement. In particular the fine granularity of the location data, with GPS accuracy down to 10 meters, and the worldwide scale of Foursquare adoption are unprecedented. In this paper we study urban mobility patterns of people in several metropolitan cities around the globe by analyzing a large set of Foursquare users. Surprisingly, while there are variations in human movement in different cities, our analysis shows that those are predominantly due to different distributions of places across different urban environments. Moreover, a universal law for human mobility is identified, which isolates as a key component the rank-distance, factoring in the number of places between origin and destination, rather than pure physical distance, as considered in some previous works. Building on our findings, we also show how a rank-based movement model accurately captures real human movements in different cities

Improved pedestrian sight-distance needs at railroad-highway grade crossings

© 2016 American Society of Civil Engineers. This paper presents an improved model for pedestrian crossing time that is used to establish preliminary guidelines for lateral clearance needs on railroad-highway grade crossings. The improved model includes new elements that are lacking in existing models such as pedestrian observation-reaction time, length of pedestrian unit, and safety margin. A general model for the required lateral clearance, that is applicable to any number of tracks on crossings located on horizontal curves or on tangent sections, was developed. The model can be used to determine the required lateral clearance to the right and to the left of the crossing, including maximum lateral clearance, its location, and lateral clearance at a specified location. A comparison of pedestrian crossing sight distance with intersection (vehicle) sight distance shows that lateral clearance needs for pedestrians are not generally satisfied by those currently available for vehicles. The presented design guidelines promote pedestrian safety and should be of interest to highway and railroad professionals

Analyzing dynamic curve widening on forest roads

Forest roads require important design specifications to ensure all-season access for various vehicles. Long and heavy log trucks can face serious maneuvering problems on forest roads due to insufficient amount of area to the left for road widening on horizontal curves. In order to provide safe and continuous shipment and transportation, appropriate curve widening areas should be provided for long vehicles along horizontal curves. In this study, a statistical model was developed to provide curve-widening solutions for long trucks (e.g., those with 18 wheels) considering various curve radius and deflection angles. The dynamic curve widening feature of Plateia 2013 program was employed to calculate curve widening for the specified vehicle. During the solution process, nine different horizontal curve diameters from 10 to 50 m (by 5 m intervals) and 17 different deflection angles from 90A degrees to 170A degrees (by 5A degrees intervals) were evaluated to run horizontal curve-widening analysis. Using a multiple regression model, we made suitable predictions about curve widening. The curve-widening areas decrease as the horizontal curve radius increases, while increasing the deflection angle on horizontal curves increases curve widening areas. Clearly, the computer-based dynamic curve widening model developed in this study can be effectively used in determining optimum widening for horizontal curves by evaluating the number of alternatives that fit geometrical specifications and vehicle types