Yasuhiro Kaneda

Application of Road Visibility Information System to Winter Maintenance

A road visibility information system (RVIS) was developed that uses images transmitted by multiple closed-circuit television (CCTV) cameras as road visibility information. Feasibility studies in the daytime during the winters of 2005 to 2006 and 2006 to 2007 were performed on national routes 230 and 231. During those two winters, the RVIS calculated visibility scale and road visibility index (RVI) automatically, accurately, continuously, and in a timely manner from road images recorded by multiple CCTV cameras. The RVIS processed 90% of the images transmitted by 14 CCTV cameras. The RVIS provided areawide visibility information in many formats and through many kinds of media and devices. On the basis of stored road visibility data, the finding was a high correspondence between the RVI and the subjective visibility evaluation for the same road images. In addition, this study demonstrates that the RVI monitoring website and e-mail alerts can speedily and reliably inform road administrators of snowstorm-induced poor visibility. The RVIS has the potential to collect data on road visibility reliably during daytime using images transmitted by multiple CCTV cameras. However, it is necessary to improve data collection at night and to capture still images accurately and quickly.

Method of processing closed-circuit television digital images for poor visibility identification

This study proposes a method for identifying poor visibility under adverse weather conditions by processing closed-circuit television (CCTV) digital images. The weighted intensity of the power spectrum (WIPS) was examined to determine its applicability as a value for the identification of poor visibility. The magnitude of WIPS represents the difference in spatial frequencies within the image on the basis of the human contrast sensitivity function. WIPS was calculated by the following image-processing procedure: the spatial frequency of the cutout image was calculated with a two-dimensional Fourier transform, and the power spectrum of the cutout image was calculated; WIPS was totaled at spatial frequencies that ranged from 1.5 to 18 cycles per degree. Two kinds of experiments were performed to determine whether WIPS represented the subjective visibility assessment values (SVAVs) given by the test subjects. Clear linear relationships between WIPS and SVAVs were found in both experiments. In addition, the tw...

FACTORS INDUCING MULTIVEHICULAR COLLISIONS DURING VISIBILITY REDUCED BY SNOWSTORM

Many factors are thought to relate to the occurrence of multivehicular collisions during snowstorm. These factors were analyzed by using a database and observations of multivehicular collisions. In addition to severe road weather conditions and surrounding environment during snowstorm, the drivers’ driving attributes and the traffic factors also were found to relate closely to such accidents. From these results the risk factor level was examined to assess the occurrence risk of multivehicular collision. When these risk factor levels were applied to collision cases, they closely expressed the occurrence risk. Although many challenges remain in developing a quantitative evaluation method of risk assessment, the factors identified in this study enable objective assessment of the risk of multivehicular collisions during snowstorm by consideration of the road weather, environmental, and traffic conditions of the site.

Current State of Pedestrian Slip-and-Fall Accidents in Winter in Sapporo and the Characteristics of Icy Sidewalk Surfaces

Pedestrian falls in winter in Sapporo, Hokkaido (Japan), have been a serious problem that requires an urgent solution. Pedestrians who fell severely enough to require ambulance transport to hospitals in winter have numbered between 600 and 800 a year. Pedestrians are prone to falls on slippery, icy road surfaces. Icy surfaces on roads and sidewalks form by a process that differs greatly from that of icy surfaces of natural snow cover, because the ice on roads and sidewalks is created by the compaction, breakage and re-compaction of snow by the pressure of passing heavy vehicles and pedestrians. In this study, icy sidewalk surface slipperiness and weather conditions were monitored in January and February 2009. Sidewalk surface ice core samples were taken to survey the microstructural characteristics of the ice when the sidewalk surface was particularly slippery. The survey results identified the typical weather conditions that lead to the emergence of an extremely slippery sidewalk surface : intense snowfall of 10 cm or more, followed by a series of days with daytime positive temperatures without snowfall. They also proved that when the density of the sidewalk surface layer is 500 kg/ m 3 or greater and the surface temperature of the layer is -2°C or higher, the slippery, icy sidewalk surface is most likely to emerge.

Development of a Road Visibility Forecast Model on the Basis of a CCTV-Camera-Based Road Visibility Information System

This study proposes a model that forecasts visibility in winter on the basis of a CCTV-Camera-Based Road Visibility Information System (RVIS) that was developed by the authors to minimize winter hazards including traffic accidents resulting from snowstorm-induced poor visibility. The RVIS quantifies road images recorded by multiple closed-circuit television (CCTV) cameras along the roads to automatically apply the quantified information to pre-defined visibility indexes that indicate levels of road visibility. To quantify the road images, the weighed intensity of power spectrum (WIPS) is calculated such that its magnitude represents the difference in spatial frequencies. When road visibility decreases from snowstorm or fog, the contrast of road view contained in the CCTV camera image decreases. From WIPS values, the road visibility index (RVI) is calculated. The RVI is categorized into 4 ranks for greater understandability by users: Level l (≧500 m), Level 2 (200~500 m), Level 3 (100~200 m) and Level 4(<100 m). From the RVI ranks, road users can know the visibility level on the route where they are planning to drive. The objective of this study is to develop a visibility forecast model, utilizing the RVIS. To achieve the goal, we used the data of the WIPS values and RVI ranks recorded by the RVIS as well as 1-km-mesh meteorological data recorded by the Japan Weather Association. A feasibility study on the visibility forecast model was conducted during the winter of 2009-2010 at a 35-km section of National Route 40 in Hokkaido, Japan. In the study, 1-km-mesh meteorological data were used to estimate the WIPS values and RVI ranks a few hours ahead of time by employing a multiple-regression model and the Kalman filter. And, the relationship between WIPS data from road images as dependent variables and the meteorological data as independent variables was examined to compare the accuracy of WIPS estimation between the two models. As a result, the correlation coefficient for the Kalman filter indicated better fit than that for the multiple-regression model, thereby the Kalman filter was identified to be more applicable than the multiple-regression approach to create a road visibility forecast model.

INFORMATION-SHARING EXPERIMENTS FOR BETTER WINTER ROADS: GREATER SAPPORO WHITE-NET EXPERIMENTAL PROJECT

In January 1996, record snowfall halted urban functions for 3 or 4 consecutive days in the Sapporo, Japan, area. The Civil Engineering Research Institute concluded that lack of cooperation among the road organizations and improper provision of information to citizens aggravated the disruptions. Experiments on appropriate methods of sharing information and providing information to road users were conducted and collectively named the Greater Sapporo WHITE-NET Experimental Project. Under the project, the road information–sharing experiment has been performed since the winter of 1997–1998. Information on road maintenance and road conditions during snowstorms is shared by using an e-mail mailing-list system. In a questionnaire survey, more than 60 percent of respondents indicated that sharing information by e-mail was more effective than sharing by fax or website. The car commuter monitoring experiment was carried out to understand how car commuters change their commuting methods according to road and weather information. During the 1999–2000 winter, 31 monitors who own mobile phones that can access the Internet participated. Weather and road information was provided at 6:00 p.m. and 7:00 a.m. As a result, on February 25, when 45 cm of snow fell from night until morning, more than 10 percent of the monitors changed their transportation mode to public transportation.