T I reduction of traffic fatalities and injuries in 2010 [l].

Transcription

1 Visiosese; A Advaced Lateral Collisio Warig System Tim va Dijck ad Geert A.J. va der Heijde t.vadiick~studct.utwete.l e.a.i.vafiderheijde~s~det.utwete.l Researchcetre ADA, Cetre for Trasport Studies, Faculty of Egieerig, Uiversity of Twete Abstract- Visiosese is a Advaced Driver Assistace system which combies a lateral collisio warig system with vehicle-to-vehicle commuicatio. This paper shows the results of user eeds assessmet ad traffic safety modellig of VisioSese. User eeds were determied by meas of a web-based survey. The results show, that Visiosese is most appreciated whe it uses a light sigal to war the driver i a possibly hazardous situatio o a highway. The willigess to pay is estimated at 300 Euros. Aother cociusio based o the survey is that frequet car users wat less assistace tha less frequet drivers. Besides the user eeds the impact o traftk safety is modelled. The results are idicative ad more research has to be doe. Traffic safety effects of VisioSese o a highway were modelled by meas of a microscopic car followig ad lae chage algorithm. Twelve differet traffbc scearios were modelled with ad without Visiosese. With Visiosese o traffic coflicts occur due to lae chagig ad less lae chages are performed. Visiosese is a system that ca improve trartic safety i the future. Zder Terms- ADAS, Road Traffic Safety, Huma Machie Iteractio, Impact o Traffic Flows, Lae Chage Modellig.. 1. INTRODUCTION he Europea Uio (EU) has committed itself to a 50% T I reductio of traffic fatalities ad ijuries i 2010 [l]. Besides the sociai costs of these fatalities ad ijuries, the ecoomical costs are high. I the Netherlads it is estimated at 8 billio Euros a year (I 997). I the Netherlads 1370 crashes (27 fatalities) were re corded as a result of mergig ad lae chagig i 2003, which is approximately 4% of all accidets [2]. Researchers estimate that lae chage crashes accout for 4 to of all crashes i the USA [3]. I 1991 more tha 80 percet of the crashes were property-damage-oly ad oly 0.5% of the traffic fatalities were due to lae chage/merge crashes [4]. The traffic delay due to lae chagelmerge crashes is estimated at 41.2 millio hours i 1991, which is about of the total crash-caused delay [5]. Surprisigly, most drivers i a lae chage crash do ot attempt a collisio avoidace maoeuvre. They seem to be uaware the other vehicle [6]. Huma recogitio failure is oe of the causes i 75% of lae chagejmerge crashes [7]. Supplyig the driver with more iformatio about possible hazards ca help reduce lae chageimerge crashes [5]. Advaced Driver Assistace (ADA) systems are oe of the possibilities to improve traffic safety [8], besides ifrastrctural improvemets. Subject of the paper is a ADA system, called Visiosese which combies lateral collisio warig ad vehicle-to-vehicle commuicatio (V2V). The results of a exploratory research o the user eeds ad the traffic safety effects (o a highway) of Visiosese are preseted. 11. SYSTEM OVERVIEW Visiosese combies lateral collisio warig with a V2V commuicatio system ad assists drivers while makig a lateral movemet (e.g. lae chagig or mergig) with warig sigals if It detects a vehicle i the driver s blid spot. This fuctio of Visiosese ca be compared to stadard blid spot detectio systems. Visiosese is also able to detect upcomig vehicles with very high speeds. The ability to commuicate with other vehicles is the extra feature which VisioSese offers, as compared to covetioal blid spot detectio systems. This is best described with a example. While drivig i the left lae of a highway, a driver wats to pass a vehicle which is i the right lae. However, this vehicle uexpectedly wats to perform a lae chage (the idicator is tured o}, thus creatig a potetially hazardous situatio. If the other vehicle is also equipped with Visiosese, it will detect your car ad war the driver. At the same time the Visiosese of the overtakig vehicle receives a (feedback) sigal that the driver i frot has bee wared about your presece, which meas the other driver ca avoid a accidet. The first compoet of Visiosese is lateral collisio wamig. Lateral collisio wamig systems are developed to prevet accidets caused by lateral movemets, Ihe lae chagig, mergig ad overtakig. A specific example of lateral collisio wamig systems is blid spot detectio. At this momet, several of those systems are available. Some of these systems will be itroduced o the market soo (e.g. Blid Spot Iformatio System by Volvo), but the majority are still i the developmet stage. Blid spot detectio is the most importat fuctio of VisioSese. Assessmet of user eeds has bee performed to reveal if more fuctios are desirable. With a system like VisioSese the objective is to detect obstacles which are ot i the direct view area of the driver. This meas that the side ad backwards scaig detectors are the most importat. For VisioSese is opted for CCD cameras itegrated i both outside mirrors, ad microwave radar, mouted i the vehicle rear bumper. A frotal CCD camera (which also ca used be for ACC applicatios) is optioal. The desig of this Visiosese applicatio is based o the LACOS project [9, IO]. This project evaluates differet sesors which were choje after a user eeds assessmet about critical lateral movemets 191. Based o drivers requiremets a set of sesors was built ito three test vehicles /$ IEEE

2 V2V commuicatio systems are still i a more premature state because of several limitatios. First commuicatio has preferably to take place i a etwork without beacos (a ad hoc etwork), but developmets i this area are quite recet. Secod, the techique used for commuicatio has to be uiform ad uique. Third ad last, after itroductio it will take several years to obtai a satisfyig grade of peetratio; full peetratio may take decades. The desig of the V2V commuicatio compoet of Visiosese is based o the Cartalk2000 project [I I]. I Cartalk2000, three differet groups of promisig V2V commuicatio systems ca be distiguished: Iformatio ad Warig Fuctios (IWF), Commuicatio Based LogitudiaI Cotrol (CBLC) e Co-operative Advaced Driver Assistace (CODA). Visiosese has a lot i commo with the last group of systems, because it also itegrates a ADA system with V2V commuicatio. Figure 1 shows the kctioal architecture which is suggested i [Ill. The system cetre is the O board processig uit which aalyses ad iterprets the gathered data, ad decides whether to take actio or,ot. The Localizatio uit is used for geeratig positio data ecessary for supportig the V2V applicatio. The Telematics uit supports various telematics fuctios, icludig the blid spot detectio ad the HMI. O Board Figure 1 Fuctioal Architecture CARTALKZOOO [ 11) The Vehicle Sigals uit gathers data from the board computer ad from additioal i-vehicle sesors. The Commuicatio uit deals with receivig data from ad trasmittig data to other vehicles. Commuicatio preferably takes place i a ad hoc etwork for which a ope radio etwork is used. I [ 1 I] a system is proposed based o a UMTS terrestrial radio access etwork (UTRA) ad which operates i a time divisio duplex (TDD). I Europe the frequecy bad betwee 2.01 ad 2.02 GHz is reserved for the use by UTRA-TDD, The last compoet of VisioSese is the HMI. If a hazardous situatio is detected, it is importat to preset this iformatio i such a way that the driver will otice the sigal. Besides, the sigal should ot disturb a driver i such a way that he would be iclied to tur off Visiosese. The best solutio for the HMI has bee determied from the results of the survey i the chapter User Needs. Four alteratives for the HMI were preseted i the survey. These alteratives are: soud sigals, light sigals, haptical sigals ad sigals o a display.., I. USER NEEDS A. It~.oduc6io Visiosese is primarily beig developed for highway traffic. Withi this framework the user eeds were assessed. For this purpose a web based survey was desiged. The objective of this survey was to get aswers o the followig questios: 0 I what situatios is VisioSese most usable? What is the best solutio for the HMI? 4 What is the willigess to pay for Visiosese? The survey cosisted of29 questios (23 multiple choice ad 6 ope questios); there were 263 respodets of whom 70% me ad 30% wome. The average age was 33 years. Car usage was also determied. Almost 60% used their car at least three times a week. 2 I % drove more tha 30,000 km per year, which idicates that the sample cotais a group of log distace commuters ad travellers with a busiess motive. The first five questios of the survey, dealt with characteristics of the respodets. Oe of the objectives of the survey was to discover if specific categories of respodets would differ sigificatly from other categories. The Kmskal-Wallis test (ordial data, k-idepedet samples) was used to determie the differece of the,medias of the various categories of respodets. The 0-hypothesis that categories do ot differ is tested at a 95% cofidece level. Whe it is stated that groups differ, the 0-hypothesis is rejected. B, Trafjk*icsifuaiioos The secod part of the survey was used to fid out what the usability of VisioSese is. The questios i this part were differetiated to type of maoeuvre, warig- or feedback sigal ad traffic sceario (highway or urba). Aalysis of the results (figure 2) shows that Visiosese is most usable whe it provides a warig sigal durig a highway lae chage. The feedback sigal durig a highway lae chage is also rated positive, but ot as much as the warig sigal. The same coclusios ca be draw for highway mergig. However, the differece betwee the ratig of the warig ad feedback sigal is smaller. The differece betwee the usability of warig ad feedback sigals ca be explaied from the aswers to the ope questios. Some respodets say That a warig sigal is oly desirable i case of misiterpretatio of the surroudig traffic. They expect to be distracted by the feedback sigal, especially if those sigals occur frequetly. Less frequet drivers cosider VisioSesc more usable o itersectios ad i urba traffic tha frequet drivers. I urba traffic female drivers also appreciate Visiosese more tha male drivers. Respodets also had to state i what other situatios Visiosese might be useful. Two suggestios were frequetly give. Oe was for Visiosese to assist drivers parkig their vehicles, the secod was to desig VisioSese i such a way that it also ca detect cyclists ad moped drivers. ThiS is typical for the Netherlads because 26.5% ofall trips are by bike (7.3% of the total umber of kilometres).

3 70% 60% 50% 30% 0% Namlg Fuedbatk Watig Feedback Wamig Warlg Slgal Slgal Sigal Sigal Sigal Sigal Hlghway Hlghway Lae Lae Paulig Omigi Mergig Mergig Chagig Chagig Iteectio ~ae Figure 2 Usability Visiosese C. Huma Machie Itegace The alteratives for the HMI are preseted i the table I. Each alterative cosists of a warig sigal ad feedback sigal, which ca be distiguished. For each alterative of the HMI the respodets were asked to idicate to what extet they would otice the sigal (figure 3) ad to what extet the sigal would disturb them (figure 4). After that, the respodets were asked to rak the alteratives, from most preferred to least preferred.. A sigal which will always be oticed, also scores high o the disturbace aspect. Haptical sigals for example, score high for perceptio, but also high for disturbace ad are therefore the least preferred alterative. Display sigals score low o both aspects ad are the secod least preferred. 1, TABLE I.. HMIALTERNATIVES Alterative Warig Sigal., Feedback sigal Light A red light ear both outside. ' A gree light ear both si als outside mirrors Soud sigals A soud sigal (a) from the lefl or right frot speaker A soud sigal (b) from the left or right frot speaker Haptical A vibratio of the steerig A light sigal ear the both sigals wheel combied with extra (outside) rear-view mirrors Sigals o a resistace while steerig to the directio of the coflict Movig sigals (icos), which Movig sigals (icos), display show the side of the coflict ad the positio of the ivolved' which show the positio of the ivolved cars From these results it ca be cocluded that light sigals i the outside mirror are a good compromise betwee the two aspects ad thus the most preferable form of' HMI. These results correspod with [3], where behaviour durig a lae chage is researched. It may be cocluded that the sigals must be located i a place where they ca readily be see. The frot view would be the logical place However, it is importat that whe the system is operatioal the sigal does ot distract the driver or might be see so ofte that it is igored. With this i mid, the outside mirrors are a potetial altemative for the locatio of the HMI, sice drivers have a relatively high proportio of glaces to these locatios i preparatio or a lae chage. 70% 80% 54% 30% 00% Soud Light Hapihl Diaulay Figure 3 The sigal is perceptible 70% 60% 50% 30% 0% _ Soud Llght HapClcal Display Figure 4 The sigal is disturbig - Iwa Strmgly&ree Db Agree iuc Disagree Od Strogly Disagree ita StroglyAgree ab Agree Oc Disagree,. ' Od Strogly Disagree; D. Willigess io pay I the last part of the survey, the respodets were asked to choose betwee VisioSese ad other car optios. Figure 5 shows that Visiosese would be preferred to luxury optios. Cruise cotrol ad a avigatio system are preferred to Visiosese; a parkig assistace system was chose as frequetly as VisioSese. These results idicate that costat assistace i daily traffic is appreciated more tha VisioSese. Aother factor may be the ufamiliarity with Visiosese i respect to cruise cotrol or a avigatio system. Whe offered the choice betwee cruise cotrol, avigatio system or leather upholstery, female drivers appreciate Visiosese more tha male drivers. Give a choice betwee with a avigatio system, less frequet drivers prefer Visiosese more ofte tha frequet drivers. 90% so% 70% Bo% 50% 3% 0% Fig1 i cc e5\ PA NS DP LU iosese vs. Other car optio The last questio cocerig the willigess to pay was a direct questio about the amout of moey respodets would sped o Visiosese. The media is 300 (the mea is 429 which idicates a skew distributio of the aswers). j I

4 E. Respodets remarks With regard to the ope questios which ask for a opiio about Visiosese, two groups ca be distiguished. The first group states that VisioSese will make the driver less alert, because they will trust o VisioSese blidly. I that case Visiosese would be couterproductive, leadig to more usafe situatios. Furthermore, this group metios that they ejoy drivig too much; hece they do ot wat a itelliget car. Other respodets welcome ay safety measure, because of the complexity of preset-day traffic. These two differet reactios are approximately equally distributed over the resposes. IV. TRAFFIC SAFETY MODELLING A. Itroductio The mai objective of this traffic safety modellig is a compariso of safety idicators of microscopic traftk without Visiosese (curret situatio) ad with Visiosese whe performig a lae chage o a highway. A microscopic model of a traffic situatio with ad without Visiosese has bee developed. Curret microscopic models assume that drivers are aware of all details of a give traffic situatio. This assumptio is questioable because drivers are ot always fully cocetrated ad, due to the blid spot or distractios, may ot see or otice a vehicle or perso. With Visiosese the driver is ideed aware of all details. A curret microscopic traffic simulatio model ca be used for modellig the lae chage maoeuvres with VisioSese. To simulate the situatio without Visiosese this model has to be modified. This modificatio is preseted here. Oly the lae chage support system ad the warig sigal have bee modelled. B. Traflc situatio Figure 6 shows the trafic situatio that has bee modelled. A highway sectio with six passeger cars i a right had drivig regime o two laes without oramps,is preseted. The two laes have bee modelled idepedetly; the acceleratio of a vehicle depeds oly o the vehicles ahead i the same lae. Oly free lae chage maoeuvres fiom the right lae to the left lae have bee modelled. Free lae chages are lae chages which are ot caused by approachig a exit or due to a dimiishig umber of laes. Whe a lae chage maoeuvre was completed or the lag vehicle had completely passed the subject vehicle the simulatio eds. C. Model choice Cosiderig the traffic situatio two compoets have to be modelled. First the acceleratio, speed ad positio of the followig vehicles i both laes, ad secod the lae chage maoeuvre of the subject vehicle. Several car followig algorithms exist for the first compoet. i this research the car followig part of the MIXIC algorithm has bee used to model the acceleratio, speed ad positio [12]. The MIXIC algorithm is based o the Liearmelly model which is derived from the basic Geeral Motors model [ 131. The free lae chage part of the MIXIC algorithm is used to model the secod compoet; the lae chage maoeuvre. The actual duratio of the lae chage maoeuvre is modelled by a delay of 1 secod. MlXIC has bee calibrated o a Dutch highway usig loop detector data, which is the mai reaso for choosig this the algorithm for both compoets. The model is implemeted i Matlab 6.5 ad Simulik usig a fixed time-step of 0.01 s. D. The algorithm The prefrot vehicle is modelied by the free-drivig model of MIXIC, see (1). The frot ad subject vehicle are modelled by the free-drivig ad the car-foilowig algorithm, the most restrictive acceleratio is take. The. acceleratio is limited betwee the maximum comfortable acceleratio ad the maximum comfortable deceleratio, respectively 3 d s2 ad -5 d S 2. The free-drivig model is described by (1) ad (2), the parameters are described i Table 11. e=vref-v(f-f,) (1) a,ej-v = K 1 e(abs(e/vref) > 0.03) = O(abs(e/ vrg) 50.03) (2) TABLE I1 ALGORITHM PARAMETERS FREE DRIVING AND CAR-FOLLOWING Parameter Descriptio Driver s desired acceleratio for free drivig (m/s2) The speed error ( ds) Driver s desired speed Driver reactio time (s) (set at 0.5, with stadard deviatio of 0.05) Speed(m/s) at curret time mus t, Driver s desired acceleratio for car followig (mi& Desired distace headway as a fuctio of speed(m) Costats(set at 3, 0.25 ad 0.02, respectively) Deviatio from desired distace(m) Speed ad acceleratio respectively o curret time. (ds),(ds2) Distace headway at curret time mius t, Relative speed to frot vehicle at curret time mius t&ds) Relative speed to prefrot vehicle at curret time mius t, W S ) Costat factor for distace deviatio (set at 0.3) Costat factor for speed deviatio frot vehicle(set at 1.5) Costat factor for speed deviatio prefrot vehicle(set at 7) Figure 6 Traffic situatio

5 The car-followig algorithm is described by (3), (4) ad (5). (3) The free larie chage algorithm cosists of two steps. The first decides if the subject iteds to perform a lae chage. The secod step is to evaluate the safety of the iteded lae chage. The parameters are described i Table 111. Step 1 Lae chage is iteded if (6) ad (7) are both true. (4) a < 0 to follow,frot vehicle (4) a < %--=om OR '@at ' 0*95 "subject OR 'subject < 'ref (7) Step 2 Lae chage is performed if also the safety is judged positively, that is (9) are true. Whe both steps are true for I secod the lae chage is completed ad the simulatio eds. TABLE 111 ALGORITHM PARAMETERS LANE CHANGE MODEL radom geerated umber is above 0.3 (the left blid spot probability), if it's lower, the (9) is ormally computed. F. Safety idicators Traffic safety is difficult to estimate. Accidets do ot occur frequetly eough to use statistical approaches. I stead of accidet data, traffic coflict data ca be used to give a estimate of traffic safety However, a causal relatio betwee coflicts ad accidets is difficult to prove. The time-to-collisio (TTC) is ofte used i research o ADA systems to describe safety of a traffk situatio [14]. TTC is the time required for two vehicles to collide if they cotiue o their curret speed ad path [3]. Miderhoud ad Bovy I141 suggest a TTC warig criterio of 3 secods. A TTC betwee the lag ad the subject vehicle of less tha 3 secods is called a coflict, at time of lae chage. Besides the TTC value the distace headways betwee the subject ad the three earest vehicles is estimated. A coflict is defied as a TTC shorter tha 3 secods or distace headway shorter tha 5 metres. G. Traffic scearios Research o lae chage behaviour i the USA revealed that 45% of the highway lae chages were due to a slow frot vehicle [3]. The frot vehicle is set to a desired speed of 22 d s (79.2 kmih). The speed characteristics of the scearios are preseted i Table IV. Each sceario is modelled with three startig distace headways betwee each vehicle per lae (200, 100 e 50 meters). I all, twelve variats are modelled. Each variat is simulated with 10 radomly geerated reactio times. a Parameter V&", VNbjCC! vw dmf did dw Descriptio Driver's deceleratio at curret time(m/s2) Normal comfortable deceleratio (m/s2), which is half of maximum deceleratio,which is -5 m/sl Spced of frot vehicle at curcet time(m/s) Speed of subject vehicle at curret time(m/s) Driver's desired speed(mis) Desired distace headway as a fuctio of speed(m), from (3) Distace headway betwee lead ad subject vehicle(m) Distace headway betwee lag ad subject vehide(m) E. Mod$catio of the Iae chage algorithm The perceptio of distace headway betwee subject ad lag vehicle is a importat part of the lae chage decisio. This will be subject of the modificatio. Oe of the possibilities to modify the algorithm is whether the subject vehicle has actually see the lag vehicle prior to the lae chage. I [3] the probability of a glace i a period of 3 secods prior to a lae chage is estimated, It is assumed that the lag vehicle ca oly be see whe lookig at the left blid spot ad that the lag vehicle has ot bee remarked before the 3 secods prior to a lae chage. The left blid spot glace probability of 0.3 [3] is implemeted i the lae chage model by a modificatio i (9), oly for the situatio without Visiosese. Equatio (9) is set true, if a TABLE IV TRAFFIC SCENARIOS Sceario Dcscriptio vsza v*f (ds) (ds) A Prefrot Frot Subject PreIead Lead Lag B same as A except SUblCCt C same as B except Lead Lag same as A cxccpt Lead Lag H. Results The results of the modellig are preseted i table V. Oly the results of the scearios where a lae chage was performed are displayed. The time whe a lae chage is performed, is a average of the 10 simulatios. Sceario A with startig distace headway betwee the vehicles of 200 meter is coded as A200. I scearios A50, C50 ad DIOO, o lae chage is performed i four out of te simulatios due to the left blid spot giace probability. I these scearios, the average lae chage time is based o the six simulatios where the lae chage is performed. With Visiosese fewer lae chages are

6 performed tha without the system, because the driver is aware of the positio of the vehicles behid him. I sceario B o lae chages are performed at all, this ca be explaied by the small speed differece betwee subject ad frot vehicle. The results show that with VisioSese traffic coflicts due to lae chages ca be avoided. TABLE V MODELLING RESULTS Without Visiosese With Visiosese Sceao Lae Chage at Coflict Lae Chage at (s) (s) Coflict A200 12,7 No 12,7 No AI00 4,O No 48 No A Yes No lae chage No C50 3,9 Yes No lae chage No DlOO 4,O Yes No lae chage No I. Discussio The proposed modificatio to the lae chage algorithm has a positive ifluece o the effect of VisioSese, but it is a way to simulate the differece betwee a car with ad without Visiosese. The modificatio has ot bee validated with real data. This should be subject for firther research. Aother subject for future research is the iteractio ad behaviour of drivers due to V2V-commuicatio.Tcstig this with a drivig simulator would be the most appropriate approach. V. DlSCUSSION/ CONCLUSION The scope of this research was determied as exploratory ad future research o Visiosese is eeded to get a better picture of the effects of Visiosese. A test i a drivig simulator will eable users to give a well fouded opiio, ad will give more isight ito the possibilities of V2V commuicatio. I additio, the drivers behaviour durig the test will also provide better iput for traffic safety modellig. From the reactios to the survey it ca be stated that VisioSese has potetial as a lateral collisio warig system. The ability to commuicate with other vehicles offers a lot of opportuities. However, for the users it is hard to judge o Visiosese, because of their ufamiliarity with V2V commuicatio. With VisioSese less coflict situatios occur i lae chagig. Therefore it ca cotribute to the targets ofthe EU to improve traffic safety. Besides the drivig simulator test, the techical implemetatio (Iikig V2V ad lateral collisio warig) of Visiosese has to be realized. Before itroducig Visiosese o the market a field test with equipped vehicles is ecessary the Uiversity of Twete, the Netherlads. AIDA is realised by TNO ad the Uiversity of Twete. Its aim is to carry out iovative research ad to educate studets i the field of driver support systems. The authors would like to thak prof. dr. ir. I3. va Arem ad ir. T.J. Muizelaar for their support durig the project. REFERENCES EC (2003), Fial Report of the esafety Workig Group o Road safety, Luxembourg, SWOV, Ogelukkedatabase [Accidet database]. Leidschedm Available ofie: S.E. Lee, E.C.B. Olse, W.W. Wieville,(2004) A Comprehesive Examiatio of haturalistic Lae-Chages, Virgiia Tech Trasportatio Istitute I Natioal Highway Trasportatio Safety Admiistratio, Blacksburg, VA, J.S. Wag, R..R, Kiplig, (1994) Lae chageherge crashes: Problem size assessmet ad statistical descriptio, Natioal Highway Trasportatio Safety Admiistratio, Washigto, DC, J.D. Chova, L., TIJeria, G., Alexader, D.L. Hcdricks, (1994) Examiatio of Lae Chage Crashesad Potetial IVHS, Departmet of Trasportatio Research ad Special Programs Admiistratio, Cambridge, MA, Tijeria, L., (1999). Operatioal ad behavioral issues i the comprehesive evaluatio of lae chage crash avoidace systems. Joural of Tsportatio Huma Factors, 1(2), Kiplig, R. R. (1993). IVHS techologies applied to collisio avoidace: Perspectives o six target crash types ad coutermeasures. I Proceedigs of the 1993 Aual Meetig of IVHS America: Surface Trasportatio: Mobility, Techology, ad Society ( ). Washigto, DC. Lu, M., K. Wevers, R. va der Heijde, ad T. Heijer (2004). ADAS applicatios for improvig traftic safety: the potetial effectiveess of a iovative strategy regardig behavioural chage. i Proceedigs IEEE SMC 04, The Hague, October J. Mihm, S. Becker, M. Brockma, Y. Hofma, C. Fiche da Silva,(200) User Cetred Evaluatio of ihe LACOS System- Mzthdology ad Results, 7th World cogress o Itelliget Trasport Systems, paper o.2289, Turi, Italy, A. Saccago. Dcvices ad Sesors Applied to the LACOS Architecture, 7th World cogress o Itelliget Trasport Systems, paper o.2276, Turi, Italy, P.L.J. Morsik, et al(2003). CARTALK Developmci of a Co-operative ADAS based o vehicle-to-vehicle commuicatio, 10th World cogress ad exhibitio o Itelliget trasport systems ad services, paper , Madrid, Spai, Arem, B. va, Vos, A.P. de & Vaderschure, M.J.W.A. (1997) The microscopic traffic simulatio modsl MlXlC 1.3 (Report Iro-VVG b). Delft: TNO Iro, May, AD.( 1990), Traffic Flow Fudametals, Eglewood Cliffs, New leaey: Pretice-Hall, Miderhoud, M.M. ad Bow, P.H.L., (2001). Extcded time-to-collisio measures for road traffic safery assessmet. Acc. Aal. Prev. 33, pp ,2001. ACKNOWLEDGEMENTS The Visiosese project has bee facilitated by the research cetre Applicatios of Itegrated Driver Assistace (AIDA) at - 301