2,716 research outputs found
Measuring delays for bicycles at signalized intersections using smartphone GPS tracking data
The article describes an application of global positioning system (GPS) tracking data (floating bike data) for measuring delays for cyclists at signalized intersections. For selected intersections, we used trip data collected by smartphone tracking to calculate the average delay for cyclists by interpolation between GPS locations before and after the intersection. The outcomes were proven to be stable for different strategies in selecting the GPS locations used for calculation, although GPS locations too close to the intersection tended to lead to an underestimation of the delay. Therefore, the sample frequency of the GPS tracking data is an important parameter to ensure that suitable GPS locations are available before and after the intersection. The calculated delays are realistic values, compared to the theoretically expected values, which are often applied because of the lack of observed data. For some of the analyzed intersections, however, the calculated delays lay outside of the expected range, possibly because the statistics assumed a random arrival rate of cyclists. This condition may not be met when, for example, bicycles arrive in platoons because of an upstream intersection. This justifies that GPS-based delays can form a valuable addition to the theoretically expected values
Multiple Object Tracking in Urban Traffic Scenes with a Multiclass Object Detector
Multiple object tracking (MOT) in urban traffic aims to produce the
trajectories of the different road users that move across the field of view
with different directions and speeds and that can have varying appearances and
sizes. Occlusions and interactions among the different objects are expected and
common due to the nature of urban road traffic. In this work, a tracking
framework employing classification label information from a deep learning
detection approach is used for associating the different objects, in addition
to object position and appearances. We want to investigate the performance of a
modern multiclass object detector for the MOT task in traffic scenes. Results
show that the object labels improve tracking performance, but that the output
of object detectors are not always reliable.Comment: 13th International Symposium on Visual Computing (ISVC
CT-Mapper: Mapping Sparse Multimodal Cellular Trajectories using a Multilayer Transportation Network
Mobile phone data have recently become an attractive source of information
about mobility behavior. Since cell phone data can be captured in a passive way
for a large user population, they can be harnessed to collect well-sampled
mobility information. In this paper, we propose CT-Mapper, an unsupervised
algorithm that enables the mapping of mobile phone traces over a multimodal
transport network. One of the main strengths of CT-Mapper is its capability to
map noisy sparse cellular multimodal trajectories over a multilayer
transportation network where the layers have different physical properties and
not only to map trajectories associated with a single layer. Such a network is
modeled by a large multilayer graph in which the nodes correspond to
metro/train stations or road intersections and edges correspond to connections
between them. The mapping problem is modeled by an unsupervised HMM where the
observations correspond to sparse user mobile trajectories and the hidden
states to the multilayer graph nodes. The HMM is unsupervised as the transition
and emission probabilities are inferred using respectively the physical
transportation properties and the information on the spatial coverage of
antenna base stations. To evaluate CT-Mapper we collected cellular traces with
their corresponding GPS trajectories for a group of volunteer users in Paris
and vicinity (France). We show that CT-Mapper is able to accurately retrieve
the real cell phone user paths despite the sparsity of the observed trace
trajectories. Furthermore our transition probability model is up to 20% more
accurate than other naive models.Comment: Under revision in Computer Communication Journa
WiDEVIEW: An UltraWideBand and Vision Dataset for Deciphering Pedestrian-Vehicle Interactions
Robust and accurate tracking and localization of road users like pedestrians
and cyclists is crucial to ensure safe and effective navigation of Autonomous
Vehicles (AVs), particularly so in urban driving scenarios with complex
vehicle-pedestrian interactions. Existing datasets that are useful to
investigate vehicle-pedestrian interactions are mostly image-centric and thus
vulnerable to vision failures. In this paper, we investigate Ultra-wideband
(UWB) as an additional modality for road users' localization to enable a better
understanding of vehicle-pedestrian interactions. We present WiDEVIEW, the
first multimodal dataset that integrates LiDAR, three RGB cameras, GPS/IMU, and
UWB sensors for capturing vehicle-pedestrian interactions in an urban
autonomous driving scenario. Ground truth image annotations are provided in the
form of 2D bounding boxes and the dataset is evaluated on standard 2D object
detection and tracking algorithms. The feasibility of UWB is evaluated for
typical traffic scenarios in both line-of-sight and non-line-of-sight
conditions using LiDAR as ground truth. We establish that UWB range data has
comparable accuracy with LiDAR with an error of 0.19 meters and reliable
anchor-tag range data for up to 40 meters in line-of-sight conditions. UWB
performance for non-line-of-sight conditions is subjective to the nature of the
obstruction (trees vs. buildings). Further, we provide a qualitative analysis
of UWB performance for scenarios susceptible to intermittent vision failures.
The dataset can be downloaded via https://github.com/unmannedlab/UWB_Dataset
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ASSESSING THE IMPACT OF BICYCLE TREATMENTS ON BICYCLE SAFETY: A MULTI-METHODS APPROACH
Compared to other modes, bicyclists are disproportionally affected by crashes considering their low mode share. There is evidence that crashes between bicyclists and motorized vehicle take place at road segments and signalized intersections where bicycle treatments (e.g., bike lanes) are present, urging for in-dept analysis of the safety impact of the various bicycle treatment types. Additionally, it is important to identify sensor types that have the potential to advance field data collection and traffic monitoring in multi-modal road environments. In this dissertation, three approaches, namely crash analysis, traffic conflict analysis, and analysis of driver speeding and glancing behavior, were implemented to investigate the safety impact of bicycle treatments at the segment- and the intersection-levels on bicycle safety. Prediction models were developed to predict bicycle-motorized vehicle crashes at road segments and signalized intersections, and traffic conflicts between straight-going bicyclists and right-turning vehicles at signalized intersections. Driver speeding and glancing behavior was analysed for the segment and the intersection levels. A mode classification framework to classify trajectories recorded using a radar-based sensor was developed to test the feasibility of using radar-based sensors in field studies. The findings of this dissertation contribute to bicycle safety research in terms of quantifying the safety impact of various bicycle treatment types and how to assess and also, by showing how to assess bicycle safety. The findings of this research have the potential to stand as a valuable tool for transportation policymakers and officials in charge of establishing safe bicycle networks
Improving Multiple Object Tracking with Optical Flow and Edge Preprocessing
In this paper, we present a new method for detecting road users in an urban
environment which leads to an improvement in multiple object tracking. Our
method takes as an input a foreground image and improves the object detection
and segmentation. This new image can be used as an input to trackers that use
foreground blobs from background subtraction. The first step is to create
foreground images for all the frames in an urban video. Then, starting from the
original blobs of the foreground image, we merge the blobs that are close to
one another and that have similar optical flow. The next step is extracting the
edges of the different objects to detect multiple objects that might be very
close (and be merged in the same blob) and to adjust the size of the original
blobs. At the same time, we use the optical flow to detect occlusion of objects
that are moving in opposite directions. Finally, we make a decision on which
information we keep in order to construct a new foreground image with blobs
that can be used for tracking. The system is validated on four videos of an
urban traffic dataset. Our method improves the recall and precision metrics for
the object detection task compared to the vanilla background subtraction method
and improves the CLEAR MOT metrics in the tracking tasks for most videos
Automatic Methodology for Multi-modal Trip Generation with Roadside LiDAR
Transportation planning based on historical data and methods has major limitations. Trip data canbe useful to increase the transportation safety of the specific sites and the process and programming
purposes. One of the challenges in this regard is data collecting to gain an accurate analysis of land
use development. The previous methods of data gathering such as human observational data
counting and automatic methods like pneumatic tubes and video camera suffers some limitations
that affect the accuracy of trip analysis which cause over mitigating or set some wrong rules and
regulations. Light Detection and Ranging (LiDAR) sensing is a powerful tool that has been vastly
used for mapping, safety, and medical applications. [1] Also, its application in transportation has
drawn attention in recent years. However, LiDAR sense is yet to be further explored in trip
generation. This study is an initial attempt to: 1) perform a LiDAR-based trip generation data
gathering for a local area in midtown, Reno, and 2) analyze the resulting data based on the GIS
software to develop a systematic plan for the case study and beyond
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