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Human Factors Design Guidelines for Advanced Traveler Information Systems (ATIS)and Commercial Vehicle Operations (CVO)

CHAPTER 7: SAFETY/WARNING GUIDELINES

This chapter provides human factors design relevant to Safety/Warning Functions of ATIS devices. Safety/Warning Functions provide warnings of unsafe conditions and situations affecting the driver on the roadway ahead. Safety/Warning Functions provide sufficient advance warning to permit the driver to take remedial action. Safety/Warning Functions provide messages related to relatively transient conditions, requiring modifications to the messages at irregular intervals. It should also be noted that mayday systems have been subsumed under Safety/Warning Functions for the purposes of the present discussion. Safety/Warning Functions do not encompass in–vehicle warnings of imminent danger requiring immediate action (e.g., collision avoidance devices).

The following design topics are included in this chapter:

EMERGENCY INFORMATION

• • Presentation of Immediate Hazard Warning Information
  • Presentation of Approaching Emergency Vehicle Information
  • Presentation of Automatic/Manual Aid Request Information

NON–EMERGENCY INFORMATION

• • Presentation of Road Condition Information
  • Presentation of Vehicle Condition Monitoring Information
  • Relationship Between ATIS Information and Roadway Signs

PRESENTATION OF ROAD CONDITION INFORMATION

Introduction: Road condition information refers to information relevant within some predefined proximity to the vehicle or its route. This information may include traction, visibility, congestion, construction activity, or weather conditions. Compared to the information conveyed by the immediate hazard information system, this function provides general information that could cover a wider geographic area and a longer time span.

Schematic Example of Presenting Road Condition Information

Important Note: The map display depicted above is provided solely to augment this Design Guideline by illustrating general design principles. It may not be suitable for your immediate application without modification.

Supporting Rationale: In Reference 1, a literature review, an analysis, and the results of applying a research–based design tool were used to identify the most appropriate display type, trip status, and display format to use when displaying road condition information. This type of information will most likely be presented to the driver under stressful driving conditions, such as congestion or bad weather. Therefore, it was determined that using an auditory alert (such as a tone or short speech message) to indicate that more detailed warning information was available would allow the drivers to access the information when they felt it was safe to do so.

Special Design Considerations: The reliability of the information presented will affect drivers' attitudes regarding this subfunction and will directly impact trust in the system. Reference 2 examined the effect of unreliable navigation information on drivers' trust of the system and suggested that information presented to the driver which is less than 71 percent reliable will reduce the amount of trust drivers place in the system. It is not known whether or not the results would be similar for information other than navigation (i.e., road conditions). However, due to the impact that road condition information might have on driver safety, it is believed that similar results would be found.

Cross References:

Use of Color Coding

Sensory Modality for Presenting ATIS/CVO Messages

Key References:

• 1. Hulse, M. C., Dingus, T. A., Mollenhauer, M. A., Liu, Y., Jahns, S. K., Brown, T., & McKinney, B. (1997). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Identify strengths and weaknesses of alternative information display formats. Washington, DC: Federal Highway Administration (FHWA–RD–96–142).

  2. Kantowitz, B. H., Hanowski, R. J., & Kantowitz, S. C. (1996). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: The effects of inaccurate traffic information on driver acceptance of in–vehicle information systems. Washington, DC: Federal Highway Administration (FHWA–RD–96–145).

*Primarily expert judgement
**Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data

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PRESENTATION OF IMMEDIATE HAZARD WARNING INFORMATION

Introduction: Immediate hazard warning information refers to information regarding the relative location of a hazard and the type of hazard. This information may include warning the driver of an accident immediately ahead or a stopped school bus. Thus, this information focuses on the location of specific localized incidents.

Schematic Example of Presenting Hazard Warning Information

Important Note: The map display depicted above is provided solely to augment this Design Guideline by illustrating general design principles. It may not be suitable for your immediate application without modification.

Supporting Rationale: In Reference 1, a literature review, an analysis, and the results of applying a research–based design tool were used to identify the most appropriate display type, trip status, and display format to use when displaying immediate hazard warning information. It was determined that a combination of alerting tones, speech messages, and icons would best present hazard warning information. The auditory modality offers an advantage for displays that are concerned with the external environment, because they can get the driver's attention regardless of where the driver is looking. Visual displays are not as effective at commanding a driver's attention. However, when used in combination with an auditory alerting cue, they can provide fast response times and detailed information. Having the information presented in a visual format allows the drivers to refer to it at their convenience and when they feel it is safe to do so.

Special Design Considerations: Reference 2 suggests that merely telling drivers about immediate hazards is insufficient. Instead, drivers should be told the nature of the hazard ahead (e.g., accident or traffic congestion). These information elements may be consolidated into one element. For example, placing a visual icon that depicts the nature of the incident at the location of the incident would be an efficient method of integrating these pieces of information. Also, whenever possible, drivers should be given information about which lanes are open (e.g., green arrows for open and red Xs for blocked). If the term "lane blocked" is used, the assumption is that the blockage is temporary, while using the term "closed" implies a long–term problem. In addition to location, type and distance to the hazard, other pieces of information which might be of interest to a driver using this function include: location where speed decreases, travel speed through problem area, and the length or area of congestion. While these pieces of information may be of interest to the drivers and may help them to decide whether or not to take an alternate route, care must be taken to present the information so that it does not distract the driver from the primary task of driving.

Cross References:

Color Contrast

Sensory Modality for Presenting ATIS/CVO Messages

Key References:

• 1. Hulse, M. C., Dingus, T. A., Mollenhauer, M. A., Liu, Y., Jahns, S. K., Brown, T., & McKinney, B. (1997). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Identify strengths and weaknesses of alternative information display formats. Washington, DC: Federal Highway Administration (FHWA–RD–96–142).

  2. Dudek, C. L., Huchingson, R. D., Stockton, W. R., Koppa, R. J., Richards, S. H., & Mast, T. M. (1978). Human factors requirements for real–time motorist information displays, Volume 1–Design guide. Washington, DC: Federal Highway Administration (FHWA–RD–78 –5).

*Primarily expert judgement
**Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data

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PRESENTATION OF APPROACHING EMERGENCY VEHICLE INFORMATION

Introduction: Emergency vehicle information refers to warning drivers of approaching emergency vehicles (i.e., police cars, fire trucks, ambulances). If the ATIS possesses reliable data on surrounding traffic and conditions, this function may also include telling the driver the appropriate action necessary to move out of the way.

Schematic Example of Presenting Emergency Vehicle Information

Important Note: The map display depicted above is provided solely to augment this Design Guideline by illustrating general design principles. It may not be suitable for your immediate application without modification.

Supporting Rationale: In Reference 1, a literature review, an analysis, and the results of applying a research-based design tool were used to identify the most appropriate display type, trip status, and display format to use when displaying approaching emergency vehicle information. It was determined that presenting an auditory tone would work best for alerting the drivers without distracting, confusing, or annoying them. Reference 2 states that the omnidirectional nature of auditory displays makes them most desirable for alert and warning messages. Verbal instructions as well as a visual display were used to supplement the alert, giving the driver any additional information which might be helpful. Reference 3 suggests that optimal display design would combine desirable features from speech displays, such as warning or alerting capability, with the spatial orientation provided by visual displays. This is supported by guidelines in Reference 4 which state that, because safety/warning messages are likely to occur with some frequency, they should be presented visually. However, they should be accompanied by an auditory alert, such as a tone, to draw attention quickly.

Special Design Considerations: According to Reference 4, the location of the hazard (e.g., approaching emergency vehicle) should always be given to the driver using words such as: ahead, behind, left, right, ahead to left, and ahead to right. It was determined that reading the text associated with the location of the hazard took less time than if drivers were to search their environment for the location of the hazard. Reference 5 found that people had the most difficult time localizing emergency vehicles which were approaching them from the front. Adding both auditory and visual cues in such situations might aid in reducing the amount of search time necessary.

Cross References:

Color Contrast

Sensory Modality for Presenting ATIS/CVO Messages

Key References:

• 1. Hulse, M. C., Dingus, T. A., Mollenhauer, M. A., Liu, Y., Jahns, S. K., Brown, T., & McKinney, B. (1997). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Identify strengths and weaknesses of alternative information display formats. Washington, DC: Federal Highway Administration (FHWA–RD–96–142).

  2. Sorkin, R. D. (1987). Design of auditory and tactile displays. In G. Salvendy (Ed.), Handbook of human factors (pp. 549–574). New York: J. Wiley & Sons.

  3. Robinson, C. P., & Eberts, R. E. (1987). Comparison of speech and pictorial displays in a cockpit environment. Human Factors, 29(1), pp. 31–44.

  4. Green, P., Levison, W., Paelke, G., & Serafin, C. (1995). Preliminary human factors design guidelines for driver information systems. Washington, DC: Federal Highway Administration (FHWA–RD–94–087).

  5. Caelli, T., & Porter, D. (1980). On difficulties in localizing ambulance sirens. Human Factors, 22, pp. 719–724.

*Primarily expert judgement
**Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data

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PRESENTATION OF VEHICLE CONDITION MONITORING INFORMATION

Introduction: Vehicle condition monitoring refers to the tracking of the overall condition of the vehicle to inform the driver of current problems as well as potential problems. Vehicular monitoring could range from reminding the driver to perform certain services (e.g., oil change) to warning the driver about current problems (e.g., engine overheating or flat tire). This system could also be interactive, allowing the driver to interrogate the system regarding the problem and possible solutions.

Schematic Example of Vehicle Condition Monitoring Information

Important Note: The graphic depicted above is provided solely to augment this Design Guideline by illustrating general design principles. It may not be suitable for your immediate application without modification.

Supporting Rationale: In Reference 1, a literature review, an analysis, and the results of applying a research–based design tool were used to identify the most appropriate display type, trip status, and display format to use when displaying vehicle condition monitoring information. It was determined that, although the driver should be warned of problems that arise while driving, more detailed information should be given once the vehicle has been stopped. The sensory modality for presenting vehicle condition information should be based on the severity of the problem. Higher priority warning messages should be presented in a way that gets the attention of the driver very quickly and gives clear cues as to the appropriate response to the problem. Medium priority messages are not as urgent and therefore do not require as fast a response time. Presenting thorough and clear information is the most important consideration for presenting this level of information. Low priority messages give the driver advisory information. Since the message is not required immediately and does not notify the driver of imminent danger, it should be presented in a manner which will not startle the driver or require too much attention.

Requirements for repeating this information are uncertain. At a minimum, such messages should be available at vehicle start–up. Drivers might also be given the option of suppressing messages, if they desire.

Special Design Considerations: Traditionally, vehicle condition information has been presented to the driver by dedicated, lighted icons. However, new ATIS functions could make it possible to present such a wide variety of information to the driver that the number of icons drivers would need to remember would be beyond the limit of their memory. Not only will the ATIS identify problems, as is currently done, but it will be able to describe the problem severity in detail and give the driver possible solutions. Text or auditory speech description can be used to present more detailed, complex vehicle condition information.

Cross References:

Color Contrast

Sensory Modality for Presenting ATIS/CVO Messages

Key References:

• 1. Hulse, M. C., Dingus, T. A., Mollenhauer, M. A., Liu, Y., Jahns, S. K., Brown, T., & McKinney, B. (1997). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Identify strengths and weaknesses of alternative information display formats. Washington, DC: Federal Highway Administration (FHWA–RD–96–142).

*Primarily expert judgement
**Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data

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PRESENTATION OF AUTOMATIC/MANUAL AID REQUEST INFORMATION

Introduction: Automatic/manual aid request information refers to a function that allows the driver to request emergency services without leaving the vehicle. This function would provide drivers with immediate access to a wide variety of roadside assistance (e.g., police, ambulance, towing, and fire department) without the need to locate a phone, know the appropriate phone number, or even know their current location. In circumstances where a manual aid request is not feasible and where immediate response is essential, this function would activate automatically.

Schematic Example of Presenting Manual Aid Request Information

Important Note: The graphic depicted above is provided solely to augment this Design Guideline by illustrating general design principles. It may not be suitable for your immediate application without modification.

Supporting Rationale: Reference 1 used a literature review, an analysis, and the results of applying a research–based design tool to identify the most appropriate display type, trip status, and display format to use when displaying automatic and manual aid request information. An assumption was made that requests for aid would come as the result of either vehicle problems, an accident, or offering roadside assistance. Therefore, this function would operate primarily while the vehicle was stationary. It was also determined that using a combination of both visual and auditory display modes might help to ensure that a message would be displayed if the vehicle were in an accident. In this case, even if one of the systems were disabled, there would be a chance that the other system would be able to display the message to the driver.

Special Design Considerations: According to Reference 2, critical messages, such as those from an ambulance dispatcher, should be presented to the driver immediately and should be able to get the driver's attention whether or not the display is actively being searched for information. Communication between the vehicle or the driver and the emergency dispatcher is essential for the effective use of this function. In the case of automatic aid requests, the vehicle will need the ability to detect, analyze, and report emergencies to the correct authorities. However, in the case of manual aid requests, the driver will be responsible for entering data concerning the specific services needed and the relative urgency of the request. In both cases, it is extremely important that the dispatcher be able to inform the drivers that their request for aid has been received and that a response is in progress.

Cross References:

Sensory Modality for Presenting ATIS/CVO Messages

Presentation of CVO–Specific Aid Request Information

Key References:

• 1. Hulse, M. C., Dingus, T. A., Mollenhauer, M. A., Liu, Y., Jahns, S. K., Brown, T., & McKinney, B. (1997). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Identify strengths and weaknesses of alternative information display formats. Washington, DC: Federal Highway Administration (FHWA–RD–96–142).

  2. Huiberts, S. J. C. (1989). How important is mobile communication for a truck company? IEEE, CH2789–6/89/0000–0361, (pp. 361 –364). Piscataway, NJ: IEEE.

*Primarily expert judgement
**Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data

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RELATIONSHIP BETWEEN ATIS INFORMATION AND ROADWAY SIGNS

Introduction: The relationship between ATIS information and roadway signs refers to the correspondence or consistency between these two forms of presenting safety/warning information. Safety/Warning information might be presented on roadway signs alone, on the ATIS alone, or on both display mediums. Notification style messages simply inform the drivers and allow them to determine the appropriate action on their own. Command style messages inform the driver of a situation and suggest a particular action to take in response to that situation.

Driver Compliance and Performance with Different Combinations of ATIS and Roadway Information

Supporting Rationale: In Reference 1, ATIS warning messages were presented to drivers using a driving simulator equipped with a reconfigurable ATIS. The visual scene was controlled to present drivers with roadway information in a form similar to the changeable message signs found on highways. In the study, driver safety and compliance to the presented information was assessed using a variety of objective (driver performance, response to the message) and subjective (rated self–confidence and trust) indices. ATIS messages, corresponding to events such as roadway curves, the presence of crosswalks, icy roadway, road construction, accidents in the lane ahead, and an upcoming high occupancy vehicle (HOV) lane, were presented to subjects. To assess the effects of the source of ATIS information, the information was made available to drivers only on the ATIS, only on the roadway, via both the ATIS and the roadway, and on neither the ATIS nor the roadway, depending on the driving trial. As seen in the figure on the opposing page, the best combination of few crashes and high rates of compliance with the messages was associated with driving trials in which the ATIS information was redundant with information presented via roadway signs.

Special Design Considerations: This design guideline is most appropriate when applied to notification (as opposed to command) messages; see also the design guideline on Message Style. Although command style messages were associated with high levels of driver compliance, they were also associated with more crashes than were notification style messages.

Cross References:

Sensory Modality for Presenting ATIS/CVO Messages

Message Styles

Key References:

• 1. Lee, J. D., Stone, S. R., Gore, B. F., Colton, C., Macauley, J., Kinghorn, R. A., Campbell, J. L., Finch, M., & Jamieson, G. (1996). Development of human factors guidelines for advanced traveler information systems and commercial vehicle operations: Design alternatives for in– vehicle information displays: Message style, modality and location. Washington, DC: Federal Highway Administration (FHWA–RD–96– 147).

*Primarily expert judgement
**Expert judgement with supporting empirical data
***Empirical data with supporting expert judgement
****Primarily empirical data

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FHWA-RD-98-057