Tests conducted by the prestressed concrete pressure pipe industry in the United States during the past four decades have been gathered and analyzed. The present industry design procedures are summarized. Test results are compared with design limits defined by AWWA C301 and these industry design procedures. The results show that the resultant prestress calculated by the present industry procedures correlates well with test results. Ratios of test loads that produce the first visible cracks, 0.005–0.010‐in. (0.13–0.25‐mm) wide cracks, the ultimate strength in three‐edge bearing load, and the burst strength of prestressed concrete pipe to the design limit loads are presented. The test results depict the ability of prestressed concrete pipe to control and limit crack width.

Real‐time X‐ray inspection for agricultural contraband has been tested during unloading of checked airline bags on international flights. Selected flights were imaged during five weeks of peak travel at San Francisco International Airport (SFO). It was shown that separating X‐raying and search in time and space was operationally feasible. All X‐ray images were digitized and stored on disk. Bags were tagged for image recall during later search. Image enhancement outlined shapes of rounded food items, such as fruits. Dried food was detected visually, using texture. Suspected bags were marked before release to passengers. Travellers carrying marked bags were identified and directed to manual search stations. Image recall at search was shown to be helpful in selecting bags and aiding search. A total, permanent system, consisting of two X‐ray inspection stations and six recall computers with video plus all required subsystems is estimated to cost $225,000, require two to three X‐ray observers/shift (plus search staff) and exhibit a mean time between failures (MTBF) of three months. Such a system would allow X ray and selection of up to 600‐800 checked bags (400‐540 travellers) per hour on a sustained basis.

Problem subgrade materials consisting of collapsible soils are common in arid environments, which have climatic conditions and depositional and weathering processes favorable to their formation. Included herein is a discussion of predictive techniques that use commonly available laboratory equipment and testing methods for obtaining reliable estimates of the volume change for these problem soils. A method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented. Relatively simple methods of evaluating potential volume change, based on results of familiar laboratory tests, are used.

This paper reports on the strength development of three concrete mixes, with and without fly‐ash, subjected to many combinations of controlled moist and air‐dry environments during the first 27 days. Mix proportions and specimen fabrication technique were selected so as to reproduce roller compacted concrete construction for pavements, with the intent to determine the effect of curing on such applications. Wet‐dry curing cycles produce sizable moisture fluctuations in the samples; however, it is shown that apparently improper curing conditions do not cause drastic compressive strength reduction, but rather affect the concrete exposed surface layer. Fly‐ash inclusion seems not to alter the sample's compressive strength development as a function of the curing cycles.

Rapid land development and the lack of adequate local streets often results in requests for access to Interstate and other limited access highways. Gaining access to an Interstate highway is a highly valued asset and is aggressively pursued by local development interests. Land access demands compete with operational needs for acceptable traffic service and adversarial proceedings often result. Requests for additional access normally require investigation and preparation of technical justification studies and summary documents examining engineering, operational, and cost‐benefit factors. A major requirement for this process is a traffic study sufficient to show the impact of the proposed interchange upon current and future service levels of the mainline facility. Traffic investigations should show the impacts of major changes in land‐use surrounding the new interchanges. Established operational and geometric design policy for interchange spacing is important. Local planning requirements also affect the decision. This paper presents guidelines and procedures for the necessary studies and reports supporting a timely decision regarding the request.

This paper presents an analysis and evaluation of vehicle flow characteristics on rural deceleration lanes. Site observations were conducted by means of video photography, tape‐switches for transmitting speed information, and, for braking information, by hidden observers. Findings indicated considerable differences between commonly accepted assumptions of the AASHTO model for deceleration lane length determination and actual vehicle behavior. Major points include: (1) Average speeds of diverging vehicles at start of deceleration lanes were lower than average speeds of through vehicles; (2) deceleration values, for deceleration in gear and while braking, were lower than values suggested by AASHTO; and (3) average initial deceleration in gear lasted three times as long as the value currently assumed for design purposes. A model was then formulated to determine deceleration lane length, based on average freeway and exit ramp running speeds.

Expressway networks in large urban areas are often tied up with increasing traffic demands from many large commercial vehicles. These traffic conditions are preventing the expressway networks from their original function of rapid and steady transport. Bottleneck sections on expressways are now being investigated to improve the situation. This report describes a traffic survey and an analytical method to determine the necessary merging length for an improvement project for the Meishin Expressway near the Tennozan and Kajiwara Tunnel. A probabilistic theory for calculating the merging lane length was developed, and the theory was applied to the expected traffic and geometric conditions of the improvement plan. A series of traffic surveys were conducted to estimate the traffic flow characteristics of the merging lane and the drivers' behavior when they are merging with traffic at high speeds. The merging lane length was determined based on the results of the traffic survey.

In recent decades, the importance of walking as a significant urban travel model in the total transportation system of an area has been recognized in the industrial nations of the West. In rapidly developing countries, however, the recognition of the importance of walking is still in its infancy; no data exist on this important mode of travel. Herein, the pedestrian and walking characteristics in Riyadh, Saudi Arabia, are studied and the influential variables of purpose, time, distance, and speed are examined. Significant variations in walking distances and speed were found to exist among pedestrians of different nationalities and different sex in Riyadh. When compared to his counterparts in urban centers of Western nations, an individual pedestrian in Riyadh, on the average, walks a significantly longer distance at a substantially lower speed. Knowledge of pedestrian characteristics could effectively assist in the optimization of policies concerning urban land use and the locational distribution of transport‐related facilities in rapidly growing urban areas of the developing nations.

The concept for a method of constructing a pedestrian hazard index is developed using the following hazard indicators: number of pedestrian accidents; pedestrian accident rate; proportion of special pedestrians crossing; noncompliance with the signal; and pedestrian/vehicle conflicts. The raw data are then converted from each indicator into a hazard value, ranging from 0 to 100. The last step assigns weights to each hazard indicator value to produce a pedestrian hazard index for each intersection. Finally, several intersections can then be compared on the basis of their respective indexes, the one with the highest index being the most hazardous.