مدل سازی سه بعدی و ارزیابی قابلیت دید رانندگان از تابلوهای راهنمای مسیر

علائم و تابلوها ضمن در اختیارگذاشتن اطلاعات و راهنمایی‌های مورد نیاز رانندگان، آنها را از مقررات حاکم بر مسیر و خطرات احتمالی پیش ‌رو مطلع می‌کنند. جانمایی اصولی تابلوها در بزرگراه‌ها و معابر شهری با در نظر گرفتن معیارهای دید، تاثیر بسزایی در یافتن به موقع مسیر و جلوگیری از سردرگمی رانندگان و در نتیجه کاهش ترافیک و تصادفات دارد. هدف این تحقیق، ارائه روشی مبتنی بر تحلیل مکانی در فضای سه بعدی، جهت ارزیابی قابلیت دید تابلوها است. ارتفاع و جهت قرارگیری تابلو، فاصله تابلو تا ناظر و زاویه افقی بین ناظر و تابلو و مساحت قابل درک از تابلو از جمله شاخص‌هایی هستند که بر قابلیت دید تابلوهای راهنمای مسیر تاثیرگذار می‌باشند. در روش ارائه شده موانع سه‌بعدی موجود در مسیر، تحت هندسه‌ی پرسپکتیو به سطح تابلو، تصویر و مساحت قابل درک از تابلو توسط رانندگان در موقعیت‌های مختلف محاسبه می‌شود. جهت ارزیابی قابلیت دید تابلو در موقعیت‌های مختلف خودرو (راننده) در مسیر حرکت، شاخص‌های مکانی از جمله مساحت محدوده مشترک  حاصل از تصویر موانع با سطح تابلو، فاصله بین مرکز تابلو و مرکزمنطقه‌ی مشترک و ترکیب مساحت با فاصله ارائه گردیده است. سپس ضمن طراحی سناریوهای مختلف حرکت خودرو در یک مسیر شبیه سازی شده و ارزیابی عملکرد هر یک از شاخص‌های مذکور، شاخص ترکیب مساحت با فاصله به عنوان شاخص دید انتخاب و وضعیت دید خودرو (راننده) در چهار کلاس ضعیف، خوب، متوسط و عالی، سنجیده می‌شود.نتایج تحقیق نشان می‌دهد، روش ارائه شده می‌تواند به عنوان یک ابزار مناسب در جانمایی بهینه تابلوهای راهنمای مسیر به کارگرفته شود.

3 Dimensional modeling and visibility estimation of road signs from drivers’ perspective

Extended Abstract Introduction  Road signs not only provide drivers with the necessary information and guidance, but also inform them of related rules and probable risks along roads. Safety of roads, and thus minimum delay and discomfort for drivers depends on traffic order. This order is only achieved if road signs can accurately guide drivers. Design of road signs have been evaluated in different fields of traffic engineering and urban design. Based on these evaluations, parameters like proper distance (distance in which a sign is legible for those driving in different speeds), and proper height (the height in which light reflection from the surface of the sign is minimized) have been introduced. Lack of a generalized method for designing and positioning of road signs, along with inadequate attention to their proper installation can cause a serious risk for drivers. Systematic positioning of road signs on highways and urban pathways with an especial attention to different criteria of sights has a significant impact on drivers’ ability to find the best route on time, and thus minimizes probable confusion and heavy traffic. Visibility in threedimensional space refers to threedimensional characteristic of different barriers along the roads. In most analytical studies, extruded objects and a perspective of the threedimensional model are simulated. In this approach, threedimensional analysis is usually performed based on an analysis in twodimensional space. As an instance, the concept of spatial openness index (SOI) was introduced in 3D space. This concept refers to the volume of space observable for an observer. SOI is measured by defining a cone in the observers’ position based on which simulation is performed. In this way, the volume of observable space will be reduced in the presence of obstacles. 3D visibility analysis is closely related to human perception. When human eyes observe a scene, distant objects appear smaller than closer ones. Thus, if this difference in distance is considered, the final simulation will be closer to reality. Distance index shows the space width scale by calculating the distance between the observer and the target. In this method, a decrease in distance results in a more comprehensive perception, while increased distance decreases observers’ ability to perceive the environment. Based on the distance to target and observer’s view angle, threedimensional projection simulates observers’ view and illustrates 3D obstacles on a 2D plane. The present study seeks to provide an approach based on spatial analysis in 3D space to evaluate the visibility of road signs.   Materials & Methods Indices like height and direction of road signs, perceivable distance and horizontal angle between signs and the observer (driver), and finally perceivable area of the signs effect the visibility of signs. In the proposed method, total area of each sign perceivable for drivers driving in different situations is calculated using projective geometry. In order to evaluate visibility of road signs for vehicles (driver) in different positions, spatial indices such as overlap area (area resulted from the reflection of barriers on the sign face), distance between the center of road signs and the center of overlap area, and a combination of overlap area and distance are presented. Then, different simulation scenarios are designed for the vehicle’s motion on a simulated roadway and the performance of each indicator are evaluated. Index of combination (combination of overlap area and distance) was selected as final visibility measure. With an increase in distance from the center of the sign, the overlap area decreases and visibility increases. In order to determine visibility, visual status of the vehicle (driver) is evaluated based on four categories: poor, good, medium and excellent.   Results & Discussion In order to simulate drivers’ vision, model spatial objects along the route and find optimal position for road signs, an appropriate analytical model is required. Results indicate that the proposed method can be used as an appropriate tool for optimal positioning of road signs along a route.