Driver Workload Research Articles

Effects of Smart Cards on Transit Operators

The results of an evaluation of the first transit smart card field operational test in California are presented. The smart card technologies deployed were radio frequency and integrated circuit contact systems, and the evaluation included the cost and productivity implications of smart cards relative to those of fare boxes as well as the perceptions of transit personnel. Data input for the evaluation came from interviews with transit personnel and onboard observations. The results indicate that smart cards work well and reliably in real-world bus operations. Passengers and transit personnel liked smart cards because they were faster and more convenient than cash fares. Smart cards could reduce passenger boarding times, vehicle downtime due to malfunctions of the fare system, and driver workload and stress. Furthermore, smart cards enhance the collection and quality of transit data.

Effects of Smart Cards on Transit Operators

The results of an evaluation of the first transit smart card field operational test in California are presented. The smart card technologies deployed were radio frequency and integrated circuit contact systems, and the evaluation included the cost and productivity implications of smart cards relative to those of fare boxes as well as the perceptions of transit personnel. Data input for the evaluation came from interviews with transit personnel and onboard observations. The results indicate that smart cards work well and reliably in real-world bus operations. Passengers and transit personnel liked smart cards because they were faster and more convenient than cash fares. Smart cards could reduce passenger boarding times, vehicle downtime due to malfunctions of the fare system, and driver workload and stress. Furthermore, smart cards enhance the collection and quality of transit data.

Workload Assessment of IN-CAB Text Message System and Cellular Phone Use by Heavy Vehicle Drivers on the Road

This study assessed the driver workload imposed by a text messaging system and cellular phone on heavy vehicle drivers under various driving conditions. Sixteen (16) professional commercial vehicle operation (CVO) licensed drivers drove an instrumented heavy truck over a 4-hour period on public roads under various conditions of ambient lighting (day or night), traffic density (light or heavy), and road type (divided or undivided). Within driving condition combinations, various levels of text message reading, cellular phone dialing, radio tuning, and communications dialogue were completed by the driver. Continuous measures were taken of visual allocation, steering and accelerator activity, speed maintenance and lane-keeping performance. Results of in-vehicle device use are presented and provide insights into useful workload measures and methods, as well as a contribution to the literature on cellular phone and in-vehicle text messaging system ergonomics.

Simulator Evaluation of Heavy-Vehicle Driver Workload

Six primary-task and four secondary-task workload measures were investigated in a fixed-base truck simulator. Twelve commercial drivers each drove twelve simulator modules, each 55,000 feet in length. Independent variables were road geometry, traffic density, and secondary task. All primary task measures except steering rate were not influenced by the addition of a secondary task. Two secondary tasks, reaction time to reading the vehicle tachometer and immediate recall of a 7-digit auditory number, provided effective measures of driver workload.

Estimates of Driver Mental Workload: A Long-Term Field Trial of Two Subsidiary Tasks

Two auditory subsidiary task measures of driver mental workload---delayed digit recall and random digit generation---were evaluated in a four-year field trial. Van pool members performed the tasks for 2-min periods while driving a mix of rural secondary roads, limited access expressways, high-density, limited-access urban drives, and downtown city streets on a daily commute from upstate New York to New York City. Data collected included the roadway being traveled, time of day, traffic conditions, vehicle density, speed, weather, brake applications, and driver's subjective difficulty rating. Subsidiary task degradation was a function of traffic density, average speed, and uncertainty (estimated by the number of brake depressions). Weather conditions moderated these variables. Unpredictability of traffic appeared to be the major determinant of perceived difficulty. The digit recall task correlated (r = 0.784) with driver ratings of task difficulty and (r = 0.808) with a calculated driver workload index based on brake actuations per minute plus the log2 of vehicle speed. Although subjective difficulty ratings correlated with subsidiary task performance and with objective criteria of traffic density and speed, some dissociation was noted. Indications of workload homeostasis were evident, as drivers appeared to modify their performance to keep workload within a comfortable range.

Demands on driver resources associated with introducing advanced technology into the vehicle

Efforts are underway to provide drivers with high-technology systems directed toward improving travel capability, safety, and comfort. In most cases, these systems cause increases in driver workload. This paper describes and ranks the driver resources that may be needed to service these in-vehicle systems, and briefly cites the literature relevant to the potential conflict between performing the primary task of driving and performing in-vehicle tasks associated with such systems.

Task analysis: driver workload and information needs : Stene, T M in Proc 24th ISATA Int Symp on Automotive Technology and Automation Florence, Italy, 20–24 May 1991. Automative Automation Ltd, Croydon, paper No. 910011 (1991) 8 pp (15 refs)

Task analysis: driver workload and information needs : Stene, T M in Proc 24th ISATA Int Symp on Automotive Technology and Automation Florence, Italy, 20–24 May 1991. Automative Automation Ltd, Croydon, paper No. 910011 (1991) 8 pp (15 refs)

Heavy Vehicle Driver Workload Assessment: Lessons from Aviation

Assessment of heavy vehicle driver workload can benefit from earlier research on pilot workload. Four workload issues are particularly salient: performance, methodology, measurement, and conceptual problems. Since an airplane is not a heavy ground vehicle, and since there are many differences between pilots and truck drivers, aviation workload tools cannot be applied to ground vehicles without some caveats. A summary of ten lessons learned from aviation workload is given.

Driver workload during differing driving manoeuvres : Hancock, P.A., Wulf, G., Thom, D., and Fassnacht, P.Accident Analysis and Prevention, 1990, 22.3, 281–290, 34 refs

Driver workload during differing driving manoeuvres : Hancock, P.A., Wulf, G., Thom, D., and Fassnacht, P.Accident Analysis and Prevention, 1990, 22.3, 281–290, 34 refs

Driver workload during differing driving maneuvers

Motorcycle-automobile accidents occur predominantly when the car driver turns left across the motorcyclist's right-of-way. Efforts to decrease this specific collision configuration, through an increase in motorcycle conspicuity, have concentrated on the physical characteristics of the motorcycle and its rider. The work reported here examines the behavior of car drivers during different driving sequences, in particular during left-turn maneuvers. An experiment is reported that used simultaneous video-taping of the driver and the forward-looking scene. Subjects followed a preset on-road course and were observed for head movements to determine the possibility of structural interference eye-blink frequency, probe-response time, and probe response error, as measures of cognitive or mental workload. In addition, the subjects completed two major subjective workload evaluations as reflections of effort directed to different components of the driving task. Results indicated that there were significant increases in head movements and mental workload during turn sequences compared to straight driving. This result of higher driver workload may be responsible for increasing the potential for detection failure. Such a propensity is also fostered by the higher structural interference that may be expected during turns. Failures to observe during turning sequences have differing outcomes depending on the presence of opposing traffic, as during the left turn, compared with the absence of such opposition, as occurs in the right turn. Also, the less conspicuous the oncoming vehicle in the left turn scenario, the higher the probability of detection failure. At the present time the least conspicuous powered vehicle is the motorcycle.

Mental load and risk in traffic behaviour

Abstract Car driving means accomplishing a variety of continuously varying driving subtasks which constitute workload on the driver. Total workload can be analysed by type; for instance, the amount of information to be processed while driving, or the effort of car control. One of the driver's main tasks is to cope with the hazards with which he can be confronted on each particular route. This task places demands on his mental capacities. Therefore, coping with hazards is part of the total workload of car drivers. Based on this premise, the following topics are discussed in this paper. (1)The mental-load approach in modelling traffic behaviour is described in some detail. (2)Procedures and results of investigations into load factors in car driving are presented, emphasizing workload by reference to hazards. These include a job-analytic study of driving behaviour, a simulation study of hazard perception, and a field study of drivers' exposure to different road conditions. (3)Hazards and risks must be percei...

Theoretical Review of the Secondary Task Methodology for Evaluating Intelligent Automobile Displays

This paper presents a review of the driving research literature in a search for evidence related to secondary task interference on driving. Driving studies employing secondary tasks fall into two broad categories: (a) studies concerned with driver workload, and (b) studies concerned with driver fatigue. A mjority of these studies lack a valid theoretical basis for the application of the secondary task technique and the particular choice of secondary task. Few of them examined mutual interference between secondary tasks and driving. Some studies, however, reported interference, implying the presence of resource competition. This should be of concern to equipment designers.

Measurement of level of service for two-lane rural highways

Rural highway capacity, level of service, and other planning criteria are based on outdated information from the United States where the operating environment and traffic conditions are often quite different from those in Canada. Much of the information on rural two-lane highway overtaking and capacity in the 1965 Highway Capacity Manual (HCM) can be traced to data collected as long ago as 1938. Rural two-lane highway capacity and overtaking concepts in use today have remained essentially unchanged since they first appeared in the 1950 Highway Capacity Manual.This paper presents the findings of an investigation into speed–volume relations, platooning, and overtaking on the primary two-lane rural highway system in Alberta, British Columbia, and the National Parks.The principal findings are: (i) there is little relation between speed and volume over the range of volume observed — up to 1700 vehicles per hour, (ii) the average speed at 1000 vph was found to be 20–25 km/h higher than that predicted in the HCM, (iii) the backward bending portion of the speed–volume curve was not observed, (iv) speed distributions at flow rates of 1200 vph showed a marked increase in speed over that in the HCM, and (v) speed distributions of free-moving vehicles indicate a higher proportion of vehicles travelling at uniform speed.The implication of the findings is that the level of service on two-lane rural highways is much higher than that given in the HCM. This, however, is not the case on most of the primary two-lane highway system in western Canada. Despite low volumes, in the 2500–5000 average daily traffic range, drivers perceive a low level of service. This is attributed to a high proportion of long distance (over 300 km), high-speed trips, in rolling terrain with restricted sight distances, through sparsely developed territory with few intermediate stops. Thus motorists spend most of their journey travelling in high-speed platoons resulting in a high driver workload and a propensity to take risks when overtaking.The paper concludes with a recommendation that a nation-wide effort be mounted to collect speed–volume, headway, platooning, and passing data over the full range of highway operating conditions on a year-round basis. A second recommendation is that provincial highway departments in Canada investigate the concept of platooning and opportunity to overtake for evaluating their two-lane highways. More attention should be given to the education and testing of drivers in the skills of overtaking on rural highways. Also proposed is an evaluation of currently accepted, safe passing sight distances, which may be inadequate for the current operating conditions and traffic mix. Alternatives to four lanes, such as alternating passing lanes with early warning signs (to inform the driver of overtaking opportunities a specified distance ahead in order to reduce driver frustration and prevent dangerous passes), need evaluation as well. The paper concludes with a comment on the possible impact of lower speed limits and vehicle control devices, such as the cruise control, on platooning, overtaking, and level-of-service measurement.

Secondary Task Measurement of Workload as a Function of Simulated Vehicle Dynamics and Driving Conditions

A driving simulator with a six-degree of freedom computer-generated display, a four degree of freedom physical motion system, and a three-channel sound system was used to determine the sensitivity of a secondary task to vehicle handling parameters and various driving conditions. Six subjects drove a simulated vehicle with normal automobile handling and another six drove with degraded handling (slow response). Steering ratio and disturbance level were adjusted within each set of six subjects. A secondary task consisting of reading random digits aloud from a single-digit dashboard display was used to assess workload. Using a technique similar to that of Knowles (1963) and McDonald (1973), it was found that workload increased significantly as disturbance level increased. Furthermore, workload increased significantly with degraded vehicle handling. In contrast, increasing steering ratio did not produce a significant change in workload. These results indicate that the secondary task method can be used to assess the major effects of simulated vehicle handling on driver workload. The secondary task used is directly transferable to test vehicles, and it allows the assessment of large changes in primary task difficulty even though direct primary task measurement may not be feasible or economical. Problems remain, however, in designing more sensitive secondary-task measures.

Sideloaders—a case study in the port industry

This report is an evaluation of a vehicle used in the port industry for handling containers. The vehicle is a self-loading lorry which both transports and stacks the containers within the port. Three aspects of the evaluation are discussed in the operating context: internal and external visibility, and the cab layouts. It is concluded that the vehicle has a restricted view to the rear, although with care this can be catered for. The design and position of the cab, however, can demand extreme and uncomfortable postures on the part of the driver. Certain anomalies in the cab control and display layouts are also briefly discussed, with a view to standardisation and a reduction of the driver's work-load. The main problem is seen as one of the integration of the driver/operator with a machine with two discrete functions. The visibility and posture problem areas are considered to stem from the compromises dictated by the nature of this dualfunction vehicle. Imperial units are retained since containers are specified by the ISO on the basis of American measures.

On the Effects of State Information on Driver-Vehicle Performance in Car Following

A control stick with a built-in kinesthetic-tactile compensatory display, which was used to give a driver information concerning his state with respect to the nearest lead vehicle, was tested in several full-scale car-following situations. System performance was evaluated for several display excitation signals by means of average tracking measures (headway variance and relative velocity variance), system dynamic response as evidenced by describing-function models, and subjects' opinion ratings. The average tracking performance and dynamic response of a driver-vehicle system, as well as a driver's workload, were substantially modified by providing him with aiding information. More consistent dynamic performance among driver-subjects was obtained, and it was established that part of the driving workload can be effectively shared by an automatic system.