Designing the Human Machine Interface of Innovative Emergency Handling Systems in Cars M anfred D A N G E L M A IE R * and P etra M A N G O L ** *Fraunhofer IAO, N obelstr. 12, D -70569 Stuttgart, **IA T, N obelstr. 12, D -70569 Stuttgart P R O B L E M S O F T H E H M I D E SIG N In the E uropean T ransport T elem atics project SA V E, a "system for the effective assessm ent o f the driver state control and vehicle control in em ergency situations" is being developed. C om ponents o f this type o f innovative em ergency handling system s are under developm ent since several years including especially driver m onitoring and w arning (B rookhuis 1991, K aneda 1994, K atahara 1995, W ierw ille W.W. 1993, 1994), and autom atic driving capabilities (C arrera 1995, N aab 1995). T he hum an m achine interface (H M I) o f the integrated system s are related w ith specific and partly new problem s concerning traffic safety on the one hand and the engineering process in the developm ent on the other hand. C oncerning traffic safety it can be said that the hum an m achine interface (H M I) o f such type o f system s is unobtrusive under norm al driving conditions. There is no necessity for any hum an m achine dialogue. T he system can be easily activated together w ith the engine. T he driver state control subsystem and the related routines w ill run in the background. T he driver w ill not be aw are o f the system under norm al driving conditions. O nly if an im paired driver state is detected by the driver m onitoring system a hum an m achine interaction m ight be required. In this case the boundary conditions for the dialogue are w orst. T he driver is in an im paired state and her/his perform ance is m ost probably restricted, both for the interaction w ith the em ergency handling system and for driving. T he ability to drive safely is therefore decreased. T he driver should thus concentrate on the basic driving functions and on the traffic situation. B ut in addition the hum an m achine dialogue is required, w hich again m ay effect traffic safety negatively. T his m eans that there m ight be the risk that those innovative system s can be counterproductive in certain situations. - 565-
T o go m ore into detail five different principle cases and related problem s can be distinguished: 1. N orm al driving conditions do not require any hum an m achine dialogue. T here w ill be som e basic system state inform ation displayed for the driver, w hich needs not to be read regularly. 2. T here is an em ergency detected by the em ergency system in the surrounding traffic via carto-car com m unication. Then the driver is not in an im paired state and therefore able to perform in an appropriate w ay. B ut if the em ergency in surrounding traffic is located nearby ahead the driver has to turn attention to the traffic situation. T here is a risk that a w arning m essage by the system m ight distract the drivers attention from the road scene. 3. T he driver m onitoring system detects an im paired but non-critical driver state. T hen the system has to w arn the driver and m ake her/him to react properly. T here m ight be also a high inform ation flow to the driver under adverse conditions. 4. T he driver m onitoring system detects an uncertain driver state. T his is the m ost critical phase for the hum an m achine interaction. T he system has to decide quickly by com m unication w ith the driver w hether to take control over the car or to leave the control to the driver. T h erefore there is not only an inform ation output to the driver required, w hich needs to be understood b ut also a driver reaction. T his m eans an inform ation input by the driver to the system, w hich she/he m ight have never perform ed before and all this in a probably critical personal situation o f the driver and an evolving critical traffic situation. 5. T he driver m onitoring system detects a critical driver state. T hen the autom atic em ergency handling functions w ill be initiated, e. g. an em ergency call w ill be sent to an em ergency centre and the car w ill be stopped autom atically. T his situation is highly dem anding fo r the technical system s but it is less critical for the influence o f the H M I design on driving safety as the driver is suspended from driving. B esides traffic safety considerations the design process itself is an im portant issue. T h e H M I as a safety relevant subsystem has to be considered early in the design process. H M I concepts have to be evaluated by users as soon as possible in order to deliver relevant input for further design decisions for the w hole system. T he HM I has to be developed in parallel w ith the developm ent o f the new system technologies for driver m onitoring, autom atic em ergency handling and com m unication. This results in uncertainty concerning the design o f other technical -5 6 6 -
subsystem s, w hich m eans that the H M I design has to start on the basis o f assum ptions. T his m eans sim ultaneous engineering is in dem and and rapid prototyping m ethods are required. A P P R O A C H F O R T H E H M I D E SIG N Figure 1 show s the basic approach chosen for the design o f the H M I o f the S A V E system. F igu re 1 : D esign process fo r the H M I o f the S A V E system Formulate basic design principles for the HMI Create verbal scenarios of external boundary conditions (e. g. market development) internal boundary conditions (e. g. results o f technical developments in the project) key design characteristics of the HMI Specify HMI functions Conceptualise and visualise the HMI on paper and with a rapid prototyping Tool Build rapid prototyping computer sim ulation of HMI Perform user tests Build mock-up and integrate in sim ulator Perform user tests Build demonstrator car Modify demonstrator car Perform user tests - s, A s a basis for the definition o f the H M I, design principles are form ulated, in order to help the H M I designers o f the SA V E device. T hey show the basic philosophy o f the interface design rather than pre-setting design decisions.. The design principles are based on general principles -567 -
o f the design o f H M Is in vehicles. T hey take the basic functions and objectives o f the SA V E device into consideration. SA V E H M I scenarios are developed in order to achieve a com m on understanding o f the H M I w ithin the project team s in an early phase o f the project. E xternal factors and developm ents, e.g. m arket trends in car design and available telem atic infrastructures are considered as well as internal factors, w hich are related to further results o f the S A V E project to form scenarios o f boundary conditions o f the H M I design. T hose environm ental scenarios are used to form basic scenarios o f the key design characteristics o f the HM I. S cenarios are pre-selected by the consortium for further elaboration of the corresponding HM I design. In the next steps a functional specification is perform ed. T he results are used as input for the conceptualisation o f the H M I design. First drafts are visualised on paper as w ell as w ith a rapid prototyping tool. This tool is also used to create com puter sim ulation o f alternative design concepts, allow ing for dem onstration as well as for user tests o f the hum an-m achine interaction under non-driving conditions. T he pointing device o f the com puter is used during those user tests. U ser acceptance o f concepts and som e aspects o f the user dialogue can be tested. A s the m anipulation and spatial arrangem ent o f displays and controls is not realistic, further user tests are required. F or this purpose a m ock-up o f one o f the selected alternatives is built first and then integrated in driving sim ulators for further testing. D riving sim ulators can offer a realistic driving task and realistic spatial arrangem ent and m anipulation o f displays and controls. T his is necessary to test anthropom etric and biom echanic aspects o f the design. E ven m ore im portant is the test o f the interaction o f the prim ary driving task and the dialogue betw een the the driver and the em ergency handling system. Those sim ulator tests provide answ ers to crucial design questions related essentially to traffic safety. B ut also driving sim ulators cannot give all final answ ers. D riving dynam ics sim ulation is m ostly m issing in the sim ulators and in other cases it is poor. A lso the perceptual situation is not realistic in the sim ulator cabin. B ecause o f the darkened cockpits perceptual ergonom ics aspects cannot be investigated. - 568 -
T hus the adjusted H M I design has to be im plem ented in a dem onstrator car, allow ing for testing o f the functions o f the integrated system under full driving conditions, gaining the required insight for the last HM I design adjustm ents. R E SU L T S A N D EX P E R IE N C E S T he integrated sim ultaneous engineering and rapid prototyping approach using product scenarios as w ell as com puter dem onstration/sim ulation o f the H M I has proven to be useful so far for the developm ent o f the in-car H M I o f innovative em ergency handling system s for passenger cars. F igu re 2 : H M I d em onstrator, accessible on the W W W T he applied scenario technique allow s for the functional specification and conceptualisation o f the H M I, w hen im portant technical decisions are still to be taken. C om puter sim ulation o f the H M I w ith the rapid prototyping tool A L TIA provides dem onstrations and facilities for user tests in an early phase o f the developm ent process. T he A L T IA dem onstrator -5 6 9 -
/sim ulator has even been m ade accessible online via a W W W site and could be used by p ro j ect partners for expert evaluations (figure 2). B oth, expert and user tests w ere p erform ed in order to analyse the deficits o f alternative HM I design concepts. The user tests and expert evaluations w ith the A L TIA sim ulation revealed w eak points o f the concept and resulted in an appropriate feedback for the optim isation o f the concepts and valuable input for future design steps. The critical issues m entioned at the outset o f the paper cannot be clarified w ith those com puter sim ulations. D riving sim ulator tests are required to evaluate the design according to traffic safety aspects. R E F E R E N C E S Brookhuis K. A., Schreivers G. et al: M onitoring D river Status through In-V ehicle P aram e ters. In: P roceedings o f the D R IV E C onference, B russels, F ebruary 4-6th, 1991 C arrera P., Innocenti G. et al: C ollision avoidance and A IC C : F unctional R equirem ents, Technological Trends, and E xperim ental Results. In: Proceedings o f the EA EC '95, Strasbourg, June 21-23rd, 1995 K aneda M., U eno H. et al: D evelopm ent o f a D row siness W arning System. In: P roceedings o f the 14th International Technical ESV C onference, 1994 K atahara S.: D river D row siness D etection by E yelids M ovem ent from F ace Im aging. In P ro ceedings o f the 2nd ITS C ongress, N ovem ber 1995, 1995 N aab K., H oppstock R.: Sensor System s and Signal Processing for A dvanced D river A ssistance. In: Sm art V ehicles J.P. Pauw elussen & H.B. Pacejka (eds.), pp 69-97, 1995 W ierw ille W.W.: US IV H S R esearch: V ehicle B ased D row sy D river D etection. 6em e entre- tiens "V igilance et transports du centre J. C artier, D ecem ber 9-10th, B ron, 1993 W ierw ille W.W.: O verview o f R esearch on D river D row siness D efinition and D river D row siness D etection. In: Proceedings o f the 14th International T echnical E SV C onference, 1994-5 7 0 -