Roger S Walker

Wavelength-Related Ride Equation

The existing equation used by the Texas Department of Transportation (TxDOT) to evaluate ride quality from measured profiles is based on measurements obtained from a rating session conducted in the late 1960s. Since its original development more than 30 years ago, a number of changes have required a reevaluation of the current equation. These include changes in vehicle design, such as improvements in vehicle suspension and handling characteristics, and the switch from the predominantly large automobiles used in the late 1960s to the smaller and more fuel-efficient midsized and compact cars of today. Additionally, TxDOT has changed the section interval used for reporting ride or present serviceability index from 0.2 to 0.1 mi. A new ride equation based on a specific set of profile wavelengths is described. In addition, possible uses of the equation for construction control and bump detection are discussed.

A practical approach to implementing line printer graphics

The capability of generating graphical images on a line printer is very desirable. Many ad hoc special purpose implementations exist that satisfy the needs of particular users. A single general purpose line printer graphics capability, however, compatible with widely distributed Calcomp pen plotter software, could eliminate the need for many special purpose implementations. An implementation approach is described for a set of subroutines which are designed to minimize storage requirements to maintain a complete graphical image. The software has been widely accepted in university, government, and industry environments to augment and occasionally replace pen plotting facilities.

Comparative Testing of Lasers for Ride Quality Measurement on Hot-Mix Asphalt Pavements

The Texas Department of Transportation (DOT) is implementing a smoothness specification based on inertial profile measurements. For quality assurance testing, this smoothness specification includes pay adjustment schedules that are tied to the average international roughness index. The acceptance criteria used in this specification are based on surface profile measurements collected with the traditional single-point lasers, which the department has been using to monitor pavement smoothness on the state highway network. Since the Texas DOT implemented its smoothness specification, developments in sensor technology have included multipoint and wide-footprint lasers for noncontact height measurements. There is a need to verify ride quality measurements from these newer lasers to assess their impact on quality assurance tests conducted under the Texas DOTs existing ride specification. This paper presents a comparison of ride quality measurements from tests conducted with various lasers on hot-mix asphalt concrete pavements. Of particular importance to this comparison is the verification of ride quality measurements determined from the lasers tested with corresponding reference profile measurements.

Modeling Real-Time Multi-Core Embedded System Using UML

The purpose of this paper is to model a real-time embedded system. This system known as the road surface analyzer will perform several tasks regarding road surface conditions based on multiple sensor readings. Many analysis algorithms are performed in real time on the collected data. The tasks to be implemented mainly depend on reconstructing road profile as well as perform texture analysis in real time. The tasks will be implemented in parallel, which leads to the use of a multi-core based embedded system. Real-time UML extensions will be used to model this system for mapping the tasks and analyzing the overall system