1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.TO PLACE A DOCUMENT ORDER: +1 (724) 776-4970 FAX: +1 (724) 776-0790SAE WEB ADDRESS http:
3、/www.sae.orgCopyright 2002 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICEJ2395ISSUEDFEB2002Issued 2002-02ITS In-Vehicle Message PriorityForewordThere is a concern that multiple intelligent
4、transportation systems may overburden drivers withinformation, and may present (i.e., display) messages that compete for drivers attention. At times, multiple in-vehicle messages are presented/displayed in close temporal and spatial proximity while in-transit. The objectiveof the ITS in-vehicle mess
5、age priority recommended practice is to help insure the orderly presentation of ITSinformation to the driver, considering both temporal and spatial restraints. Establishing an ITS in-vehicle messagepriority standard is an important step in the development of guidelines for man-machine interface (MMI
6、) systemsintegration and the improvement of driving safety. Related work is being conducted by the International StandardsOrganization (ISO).A critical decision associated with the design of intelligent transportation systems is the criteria used for prioritizingITS messages. Multiple ITS messages t
7、hat are displayed simultaneously while in-transit can overload driversinformation processing resources, resulting in decreased driving performance. Conversely, systems will not beacceptable or usable by drivers unless critical messages and information are presented in a timely manner.Message priorit
8、ization will provide the basis for selecting which set of simultaneously displayed messages,competing for the same display time and/or space, should be presented to the driver.1. ScopeThis SAE Recommended Practice applies to both Original Equipment Manufacturer (OEM) andaftermarket ITS message-gener
9、ating systems for passenger vehicles and heavy trucks. The recommendedpractice describes the method for prioritizing ITS in-vehicle messages and/or displayed information based ona defined set of criteria. Each criterion has a fixed number of levels that are used to rate/rank a givenmessage or inform
10、ation item to determine its prioritization value. The prioritization value is used to determinethe priority in which simultaneous, or overlapping, in-vehicle messages are presented to the driver.2. References2.1 Related PublicationsThe following publication is provided for information purposes only
11、and is not arequired part of this specification.2.1.1 ISO PUBLICATIONSAvailable from ANSI, 25 West 43rd Street, New York, NY 10036-8002.ISO CD 16951Road vehiclesErgonomic aspects of transport information and control systemsProcedures for determining priority of on board messages presented to drivers
12、SAE J2395 Issued FEB2002-2-3. Definitions3.1 Message PriorityOrder of presentation for two or more in-vehicle information items.3.2 Information ItemDisplayed message and/or auditory signal that is presented by in-vehicle systems. Note:May represent operating conditions, alarms, commands, or suppleme
13、ntal data for decision-making.3.3 Chunk or UnitSmallest useful piece of information that can stand alone in both meaning and context.3.4 The Information Item FilterProcess to determine if an information item is suitable for prioritization (Figure1).FIGURE 1INFORMATION ITEM FILTERSAE J2395 Issued FEB
14、2002-3-3.5 Prioritization CriteriaDimensions along which in-vehicle information items are evaluated (Table 1).TABLE 1PRIORITIZATION CRITERIACriteria LevelsSafety Relevance: The degree to which the information affects the safe operation of the vehicle.Directly Relevant:The information item contains d
15、irect safety information. Direct information includes any item that has as its primary purpose communication of information that is designed to reduce the likelihood that the driver/vehicle and/or other driver/vehicle and/or pedestrian will be injured/damaged. For example, a message relaying an immi
16、nent collision notification or accident ahead warning.Indirectly/Somewhat Relevant:The information is not directly safety relevant as defined above. However, the information, if processed and responded to by the driver, may reduce crash risk by reducing error or exposure. For example, a suggested na
17、vigation route that reduces travel time/distance, or a navigation information item that will likely reduce driver navigation error such as the distance to the next turn.Not Relevant:The information item is neither directly nor indirectly safety relevant as defined above. No known change in crash ris
18、k due to the presence of safety information, a change in exposure or a change in safety-related driver error will be realized due to the presence of the information. For example, a driving convenience feature such as an incoming call indicator on a cellular phone.Operational Relevance:The degree to
19、which the information increases the ease and convenience of the driving task, for example, by decreasing travel time and the stress associated with driving.Highly Relevant:Information that, if not received, will cause the driver inconvenience/expense such as delay, error or vehicle damage. For examp
20、le, notification of an incident ahead resulting in traffic delay, or an engine temperature warning. Moderately Relevant:Information that is not highly relevant, as defined above. Information that may improve the ease and convenience of the driving task, but will not likely result in inconvenience or
21、 expense to the driver if not present. For example, the distance to the destination on a navigation system or the price of a toll ahead. Little or No Relevance/Insignificant:Information that will not impact the ease and convenience of the driving task. For example, a mobile internet feature or the “
22、stereo” indicator on an entertainment system.Time Frame:The degree to which the information is time sensitive, that is, the immediacy with which the information is required.Emergency: 0-3 sImmediate: 3-10 sNear Term: 10-20 sPreparatory: 20-120 sDiscretionary: 120 sSAE J2395 Issued FEB2002-4-3.6 The
23、Priority Order Index (POI)An index listing every possible combination of the levels of the three criteria,which are rank ordered in terms of “priority” (Table 2).TABLE 2CRITERIA LEVEL COMBINATIONS FOR PRIORITY ORDER INDEXSafetyRelevanceOperational RelevanceTimeFrame POIDirectly Highly Emergency 0-3
24、s 1Directly Highly Immediate 3-10 s 2Directly Moderate Emergency 0-3 s 3Directly Moderate Immediate 3-10 s 4Directly Little/No Emergency 0-3 s 5Directly Highly Near Term 10-20 s 6Directly Moderate Near Term 10-20 s 7Somewhat Highly Emergency 0-3 s 8Directly Little/No Immediate 3-10 s 9Directly Highl
25、y Preparatory 20-120 s 10Somewhat Highly Immediate 3-10 s 11Directly Little/No Near Term 10-20 s 12Directly Moderate Preparatory 20-120 s 13Somewhat Moderate Emergency 0-3 s 14Somewhat Moderate Immediate 3-10 s 15Directly Highly Discretionary 120 s 16Somewhat Highly Near Term 10-20 s 17Directly Mode
26、rate Discretionary 120 s 18Somewhat Little/No Emergency 0-3 s 19Directly Little/No Preparatory 20-120 s 20Somewhat Moderate Near Term 10-20 s 21Directly Little/No Discretionary 120 s 22Not Highly Emergency 0-3 s 23Somewhat Little/No Immediate 3-10 s 24Not Highly Immediate 3-10 s 25Somewhat Highly Pr
27、eparatory 20-120 s 26Somewhat Little/No Near Term 10-20 s 27Somewhat Highly Discretionary 120 s 28Somewhat Moderate Preparatory 20-120 s 29Not Moderate Emergency 0-3 s 30Not Highly Near Term 10-20 s 31Not Moderate Immediate 3-10 s 32Somewhat Moderate Discretionary 120 s 33Somewhat Little/No Preparat
28、ory 20-120 s 34Not Moderate Near Term 10-20 se 35Somewhat Little/No Discretionary 120 s 36Not Little/No Emergency 0-3 s 37Not Highly Preparatory 20-120 s 38Not Highly Discretionary 120 s 39Not Moderate Preparatory 20-120 s 40Not Little/No Immediate 3-10 s 41Not Moderate Discretionary 120 s 42Not Lit
29、tle/No Near Term 10-20 s 43Not Little/No Preparatory 20-120 s 44Not Little/No Discretionary 120 s 45SAE J2395 Issued FEB2002-5-4. Procedure for Determining ITS Message Priority4.1 Select Prioritization EvaluatorsThe group of evaluators shall consist of at least three people from a rangeof discipline
30、s and stakeholder communities, each of whom possess a good understanding of informationsystem functions, and can objectively examine these functions from a driver perspective. 4.2 Delineate Information ItemsInformation that contains multiple pieces of information (e.g., a flat paneldisplay with a va
31、riety of information items) will be difficult to appropriately prioritize due to the likelihood thatmultiple items with differing prioritization criteria will be present at the same time. Therefore, an important partof this process shall be to delineate the information that is to be displayed into a
32、ppropriately sized information“units” or “chunks.” Examples of appropriate information items, as operationally defined as part of thedocument, are shown in Table 3.4.3 Filter the Information ItemEach information item shall be “filtered” to determine if it represents informationrequested by the drive
33、r, continuous visual status information required by the driver, or information that is to bepresented due to external/environment events. Figure 1 represents this filtering process. As shown,information requested by the driver shall be immediately displayed unless information of a more critical natu
34、redemands priority, such as a collision warning. Likewise, a dedicated portion of an in-vehicle display shall bereserved for certain types of status information that must be continuously displayed, such as vehicle speed ora high beam indicator. Remaining information items shall be presented in a tim
35、ely manner consistent withroadway, traffic and environmental events, such as relevant toll booth information, distance to the next turnalong the route, or collision warning information. These are the information items that require prioritization asdetermined through the Priority Order Index.4.4 Appl
36、y the Priority Order Index (POI)Once the information items have been filtered based on the previousscheme, the POI shall be applied to determine message prioritization. The following sections describe thattask. 4.4.1 DETERMINE SAFETY RELEVANCE, OPERATIONAL RELEVANCE, AND TIME FRAME LEVELSThe first t
37、ask shall beto decide which safety relevance, operational relevance, and time frame levels are appropriate for theindividual message. This shall be accomplished by carefully considering each information item based on theoperational definitions described in Table 1. One level must be chosen for each
38、criterion.For example, one might determine that the message “Icy Bridge Ahead” is Directly safety relevant, Highlyoperationally relevant, and requires a Preparatory time response. Note that an evaluator may assign thesame levels of each criterion to two or more information items. It is important tha
39、t the criteria only be appliedto each information item singularly; that is, the messages should not be compared against each other whenapplying the criteria.4.4.2 ASSIGN POI RANKThe second task shall be to use the POI (Table 2) to find the rank that is associated withthe combination of levels chosen
40、. Using the previous example, an information item that is Directly safetyrelevant, Highly operationally relevant, and requires a Preparatory time response corresponds to a POI rankof 10. TABLE 3EXAMPLE INFORMATION ITEMSAppropriate Information ItemsTurn right onto Poplar in 0.1 mileHeavy fog on plann
41、ed routeToll cost: $1.25School bus stopped aheadConstruction delays on Route 12Engine overheatingIcy bridge aheadSAE J2395 Issued FEB2002-6-The levels assigned for each criterion should be recorded in a simple table. An example is provided in Table4. Note that the priority order is in the final colu
42、mn. 4.4.3 DISCUSSION AMONG E VALUATORSAfter each evaluator assigns a POI rank to each item, the evaluators shallcompare their assignment of criteria levels and resulting POI ranks. In cases where a disparity is foundbetween evaluators, a discussion of the reasons for the levels of the criteria selec
43、ted should be conducted toclear up misconceptions about the criteria, the levels, or the information item. Note that it is not necessaryfor all of the evaluators to have the same rankings; however, discussion of the different level assignmentsamong the evaluators may promote clarification of the con
44、ditions under which the information item may bepresented.4.4.4 AVERAGE RANKSAfter the evaluators have determined their final criteria levels and applied the priority orderindex to the messages individually, the POI ranks shall be averaged for each message across evaluators. 4.4.5 PRIORITIZE TIESOnce
45、 the POI ranks are averaged, it is possible that more than one information item mayhave the same POI rank. For these cases, the evaluators and designers shall determine which messageswill have priority. 4.4.6 INCORPORATING NEW INFORMATION ITEMS INTO AN EXISTING RANK STRUCTUREIn the event that a newi
46、nformation item needs to be incorporated into an existing rank structure, the same technique as thatdescribed in 4.4 shall be utilized. If there is a tie between the new item and one or more existing items, theevaluators and designers shall determine which messages will have priority.PREPARED BY THE
47、 SAE SAFETY AND HUMAN FACTORS COMMITTEETABLE 4EXAMPLE APPLICATION OF PRIORITY ORDER INDEXSafety Operation Time RankDirectly Highly Preparatory 0-3 s 10SAE J2395 Issued FEB2002RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThis SAE Recommended Practice a
48、pplies to both Original Equipment Manufacturer (OEM) andaftermarket ITS message-generating systems for passenger vehicles and heavy trucks. Therecommended practice describes the method for prioritizing ITS in-vehicle messages and/or displayedinformation based on a defined set of criteria. Each crite
49、rion has a fixed number of levels that are usedto rate/rank a given message or information item to determine its prioritization value. The prioritizationvalue is used to determine the priority in which simultaneous, or overlapping, in-vehicle messages arepresented to the driver.Reference SectionISO CD 16951Road vehiclesErgonomic aspects of transport information and control systemsProcedures for determining priority of on board messages presented to driversDeveloped by the SAE Safety and Human Factors Committee
