Powered industrial vehicles, such as forklifts, are widely used in manufacturing and other industries. Potential safety issues exist due to limitations in the operator"s ability to see all around the vehicle. Areas the operator cannot see are called non-visible vehicle regions. Nonvisible regions for operators of powered industrial vehicles are mainly caused by vehicle obstructions The regions are required to meet certain criteria specified by standards. American National Standard Institute (ANSI)/Industrial Truck Standards Development Foundation (ITSDF) ANSI/ITSDF B56.5, ANSI/ITSDF B56.11.6, and International Organization for Standardization/Draft International Standard (ISO/DIS) 13564-1 standards require measurement and evaluation of visibility from powered industrial vehicles. The National Institute of Standards and Technology"s (NIST) Intelligent System Division has been researching advanced 2D and 3D imaging sensors for improving both automated and manned forklift safety. Improvements are expected to provide 3D obstacle detection for both vehicle types. It is important to understand non-visible region locations initially, since that would then determine what type of 3D imagers would be required and where the sensors would be mounted. Visibility of a forklift was evaluated at NIST by following the above ANSI and ISO standards through 11 tests which set criteria based on the patterns of shadows cast when the forklift does not carry any load. Also, new test methods were created and tested. The new test methods were based on the forklift carrying loads and using standard sized test pieces and a mannequin. The NIST experiments, tests methods, and results are detailed in this report. This report will then serve as a basis for further advanced visibility and semi-automated powered industrial vehicle safety performance measurements and test methods development.

Abstract. By use of asymptotics, we derive explicit, simplified formulas for integrals representing the force dipole interaction energy per unit length between curved line defects (steps) of the same sign in homoepitaxy. Our starting point is continuum linear elasticity in accordance with the classic model by Marchenko and Parshin (1981 Soviet Phys. JETP 52 129). We consider geometries that stem from perturbations of concentric circular steps (radial case). In the radial case, we define a small geometric parameter, δ 2 , expressing the smallness of interstep distance relative to the circle radii. We invoke the Mellin transform with respect to δ 2 and derive systematically an approximation for the requisite integral. This technique offers an alternative to an exact evaluation in terms of elliptic integrals. We then demonstrate the use of the Mellin transform when calculating the force dipole interaction energy between smoothly, slowly varying steps that form perturbations of circles. We discuss conditions by which the force dipole interaction may favor the modulation of closed step profiles.