Traffic Conflict Analysis Under Fog Conditions Using Computer Simulation

The weather condition is a crucial influence factor on road safety issues. Fog is one of the most noticeable weather conditions, which has a significant impact on traffic safety. Such condition reduces the road\u27s visibility and consequently can affect drivers\u27 vision, perception, and judgments. The statistical data shows that many crashes are directly or indirectly caused by the low-visibility weather condition. Hence, it is necessary for road traffic engineers to study the relationship of road traffic accidents and their influence factors. Among these factors, the traffic volume and the speed limits in poor visibility areas are the primary reasons that can affect the types and occurring locations of road accidents. In this thesis, microscopic traffic simulation, through the use of VISSIM software, was used to study the road safety issue and its influencing factors due to limited visibility. A basic simulation model was built based on previously collected field data to simulate Interstate 4 (I-4)\u27s environment, geometry characteristics, and the basic traffic volume composition conditions. On the foundation of the basic simulation model, an experimental model was built to study the conflicts\u27 types and distribution places under several different scenarios. Taking into consideration the entire 4-mile study area on I-4, this area was divided into 3 segments: section 1 with clear visibility, fog area of low visibility, and section 2 with clear visibility. Lower speed limits in the fog area, which were less than the limits in no-fog areas, were set to investigate the different speed limits\u27 influence on the two main types of traffic conflicts: lane-change conflicts and rear-end conflicts. The experimental model generated several groups of traffic trajectory data files. The vehicle conflicts data were stored in these trajectory data files which, contains the conflict locations\u27 coordinates, conflict time, time-to-conflict, and post-encroachment-time among other measures. The Surrogate Safety Assessment Model (SSAM), developed by the Federal Highway Administration, was applied to analyze these conflict data. From the analysis results, it is found that the traffic volume is an important factor, which has a large effect on the number of conflicts. The number of lane-change and rear-end conflicts increases along with the traffic volume growth. Another finding is that the difference between the speed limits in the fog area and in the no-fog areas is another significant factor that impacts the conflicts\u27 frequency. Larger difference between the speed limits in two nearing road sections always leads to more accidents due to the inadequate reaction time for vehicle drivers to brake in time. And comparing to the scenarios that with the reduced speed limits in the low visibility zone, the condition that without the reduced speed limit has higher conflict number, which indicates that the it is necessary to put a lower speed limit in the fog zone which has a lower visibility. The results of this research have a certain reference value for studying the relationship between the road traffic conflicts and the impacts of different speed limits under fog condition. Overall, the findings of this research suggest follow up studies to further investigate possible relationships between conflicts as observed by simulation models and reported crashes in fog areas

Setting the Width of Emergency Exit in Pedestrian Walking Facilities

AbstractTo improve the safety of pedestrian evacuation and the utilization efficiency of emergency exits in pedestrian walking facilities, the method of computing the width of emergency exits was presented in this paper. These factors of influencing the setup of exit width were analyzed from the process of pedestrian evacuation, the capacity of pedestrian passing exit and the strategy of pedestrian selecting exit. It is shown that the setup of exit width is dependent on the capacity of passing exit, the strategy of exit selection and the total sum, initial site, and aggregation degree of pedestrians in walking facilities. It is also found that the total capacity of passing exits will be low with the number of exits rising under the condition with a fixed total width of exits. The procedure of setting exit was presented to compute the number, site and width of every exit in pedestrian facilities through an example

All Dogs Go to Prince George’s County: Finding a Home for a Second Animal Services Facility

Final project for URSP 688M: Planning Technologies (Spring 2018). University of Maryland, College Park.As a continuation of the Fall 2017 PALS project, Spring 2018 semester students from the community planning and engineering programs used advanced computer mapping tools (geographic information system, or GIS) to provide Prince George’s County with potential sites to build a second animal shelter. The team attempted to find land that the county already owned, but none of the parcels met the requirements. The team found a solution to this problem by including distressed shopping centers in the site analysis. From these forty shopping centers, eleven were chosen for their location within the county’s Growth Policy Center. We used ArcGIS Online to understand how many potential adopters could reach these facilities within fifteen and thirty minutes. We then chose the five shopping centers closest to the most people and households. We present these to Prince George’s County as potential candidate sites. The link for the county to access the ArcGIS Online website to view the maps and site locations is: http://uofmd.maps.arcgis.com/home/item.html?id=ea8cc7f3ca154064939db517e24b4606.Prince George's Count

Freeway Safety Service Plan Designing and Optimization Modeling

Traffic incidents on freeways cause a considerable loss of life and property. Therefore, some organizations provide freeway safety services to improve the roadway’s safety condition by assisting in detecting and clearing incidents. Incidents generally require timely assistance in removing debris and disabled cars from roads and transferring injured persons to medical care places. However, these fast reactions require more resources such as professional staff and service vehicles from the service providers. Limited funding sources constrain these operations. Thus, it is essential to design appropriate service plans for the service providers to offer in-time assistance to road users at reasonable costs. This research aims at providing appropriate freeway safety service plans based on historical traffic incident data and freeway road networks. First, clustering methods are applied to detect traffic incident hot spots. Second, with this hot spot knowledge integration, a standby service plan is formulated by configuring the whole freeway network and building a coverage model. Experiments are conducted to assess the performances of the designed plan by several proposed metrics. The data used in these experiments is from the patrol service provided by the Coordinated Highways Action Response Team (CHART) in Maryland in 2016. The proposed service plans are compared and evaluated by several metrics that are computed from evaluation experiments. The data used in the evaluation experiments are provided by the platform of PeMS in California from the incidents they assisted in 2017 due to the lack of vehicle dispatch timestamps in the CHART data. The evaluation experiment scenarios are built based on parts of road networks served by the California Highway Patrol (CHP). The experiment results indicate that the proposed model has the potential to improve upon the current operations by reducing the total response time and using the available service vehicles efficiently

PRSS8 is Downregulated and Suppresses Tumour Growth and Metastases in Hepatocellular Carcinoma

Background: Protease serine 8 (PRSS8), a trypsin-like serine peptidase, has been shown to function as a tumour suppressor in various malignancies. The present study aimed to investigate the expression pattern, prognostic value and the biological role of PRSS8 in human hepatocellular carcinoma (HCC). Methods: PRSS8 expression in 106 HCC surgical specimens was examined by Real-time polymerase chain reaction (PCR) and immunohistochemistry, and its clinical significance was analysed. The role of PRSS8 in cell proliferation, apoptosis and invasion were examined in vitro and in vivo. Results: PRSS8 mRNA and protein expression were decreased in most HCC tumours from that in matched adjacent non-tumour tissues. Low intratumoral PRSS8 expression was significantly correlated with poor overall survival (OS) in patients with HCC (P = 0.001). PRSS8 expression was an independent prognostic factor for OS (hazard ratio [HR] = 1.704, P = 0.009). Furthermore, restoring PRSS8 expression in high metastatic HCCLM3 cells significantly inhibited cell proliferation and invasion. In contrast, silencing PRSS8 expression in non-metastatic HepG2 cells significantly enhanced cell growth and invasion. Moreover, our in vivo data revealed that attenuated PRSS8 expression in HepG2 cells greatly promoted tumour growth, while overexpression of PRSS8 remarkably inhibited tumour growth in an HCCLM3 xenograft model. Enhanced cell growth and invasion ability mediated by the loss of PRSS8 expression was associated with downregulation of PTEN, Bax and E-cadherin and an upregulation in Bcl-2, MMP9 and N-cadherin. Conclusions: Our data demonstrate that PRSS8 may serve as a tumour suppressor in HCC progression, and represent a valuable prognostic marker and potential therapeutic target for HCC