Simulator based assessment of drivers with visual field defects

1. Simulator based assessment of drivers with visual field defects Björn Peters, VTI

2. Sweden – some basic facts • EU member state • EU driving license directive – specification of minimum medical requirements • 9.6 million inhabitants • 6.1 million driving license group 1 • 1.6 million license holders +65 y • 40 000 revoked licenses (all reasons) (2013) • 4 500 revoked licenses for medical reasons annually (2013) • ?? due to visual problem • 100 applications for exemptions annually

3. Swedish requirements for peripheral visual field Group I Binocular Esterman screening test

4. ≥10 dB ≥20 dB Swedish requirements for central visual fieldGroup I Static threshold perimetry (Humphrey 24-2 or equivalent) Within 10° from fixation: Threshold in each corresponding test point should be 20 dB or more Within 20° from fixation: Threshold in each corresponding test point should be 10 dB or more (one missing point is accepted)

5. The process in Sweden • Mandatory for all physicians to report if medical requirement not fulfil or agree with the patient to refrain from driving (written consent) • Swedish Transport Agency (STA) decides if requirements fulfilled –> OK, If not -> revoked license • Agree -> apply for exemption or Disagree -> appeal in court 3 levels • Apply for exemption -> added evidence of fitness to drive required e.g. • Simulator Based Assessment in Norway - SINTEF • On-road assessment not sufficient • Demand for a new Simulator Based Assessment Method • License with exemption – conditions can apply e.g. geographical restrictions (2012 – 103, 2013 – 110)

6. Simulator test at SINTEF – reaction time 6 positions – rural road 1 Press buttons to respond 6 positions – rural road 1 Results compared to normative data 11 positions – city road 1 Reaction times were recorded from 20 stimuli over a 15 minutes drive. Stimuli size: 1. child head at 30 m, 2. adult body at 30 m, Stimuli: duration 4 seconds

7. Developing a new assessment method at VTI • Aim: determine if a driver with a visual field loss can compensate and drive equally well as a driver without field loss • Approach: develop a relevant and realistic diving task with more or less critical situations and build a matched reference database (100+) • Simulator: high end simulator, dynamic, good visual system • Consider: simulator sickness and test conditions • Output: certificate stating driving performance/ability compared to normative data • Assessment Validity: continuous follow-up and improvements

8. Simulator based assessment - pros and cons

9. VTI Driving Simulator IV - Volvo XC 60 cabin Rear- and Side- Mirror Displays 4 Video Cameras Virtual Cockpit Display Sound System Rexroth hexapod X-Y Sled 2,3 * 2,5 m Force Feedback Steering Wheel 5 Gaze Tracking Cameras Shaker

10. Sim IV visual projection system Tillfälle att prova under dagen • 9x Epson EB-410W projectors • Mersive SOL software • Auto calibration • Edge blending • Color correction • >180 degree field-of-view

11. Driving task and assesment criteria • Approx. 50 km driving (rural, motorway, city) • Critical situations (pedestrians, vehicles, bicycles, road works, traffic light etc.) • Assessment measures: speed, time, lateral position, (collisions/incidents) • Also: Time based safety margins (combination of TTC and THW) • Reaction time to artificial stimuli (SINTEF like) • Tentative assessment criteria exclude 2,5% of “low performers” (previously used at SINTEF) - several measures Tool for development, runs on a PC

12. SINTEF test - proposal • Motive: compare data with SINTEF and other studies • Stimuli as SINTEF – traffic signs in 6 different positions (false and true (STOP sign)) • Simultaneous stimuli – right/left – controlling for over compensation • Two buttons on the steering wheel • One true stimuli (also combination with false) – press one button • Two true stimuli – press two buttons • One single or two false stimuli – press no buttons • Separate part of the driving task • Clear written and oral instructions • Training before

13. Defining assessment criteria – a difficult task • Considering own and other road users’ safety • Not restrict if driving ability deemed sufficient • No solid scientific evidence for how much we need to see in order to drive safely • Other examples • Alcohol (BAC - 0,2‰) fixed – should it be differentiated? • Deafness OK to drive – why? • Epilepsy – OK with medication and no seizure for 3 months • Dementia – when is the right time to stop? • Mobility impairments – what is sufficient adaptation? • Whatever we do we need to follow-up!

14. Visual and cognitive tests • Visual acuity • Visual field of view test - Humphrey • Useful Field of View (UFOV) • Trail Making Test (TMT A&B) • Dynamic TMT (New) • Perceptual speed (Operative) • Attentional demanding (Operative/Tactical) • Working memory (Tactical/strategic) • Meta memory (Strategic) Useful field of view (UFOV) Dynamic Trail Making Test

15. Persons with visual field defects interested to participate • Until 15 April 222 interested • 189 replied a short survey • Data for recruiting 100 reference drivers • Most have sent their visual field data • Select a small, relevant group of drivers to participate in the project • Delivery date mid - 2014

16. Age, gender, experience for selection of reference drivers Most male, < 70% 55 + Min 10000 km/y Max 25000 km/y

17. Diagnoses Select based on diagnosis and visual field defect

18. Difficult driving situations

19. Questions, comments?