driving is a complex task requiring appropriate reactions to different situations on the 
 road1 and depends on intact sensory and 
 motor functions2 . driving performance is 
 adversely affected by many reasons like visual , neurological , and age - related deficits3 . therefore , formulating a fitness to drive 
 recommendation using psychological and neurological tests is important in keeping 
 potentially unsafe drivers with neurological deficits off the roads4 . various off - road tests to assess an individual s fitness to 
 drive include trail making test , stroke driver screening assessment , useful field of view 
 test , cognitive behavioral driver s inventory , driveable , clock drawing test , 
 drivesafe / driveaware , computerized sensorimotor and cognitive tests4 . among these tests , the trail making test part b ( tmt - b ) has 
 been demonstrated , by several researchers , to be a good neuropsychological test for 
 assessing fitness to drive in a laboratory environment5 . the trail making test ( tmt ) consists of part a and part b in some neuropsychological tools 
 used in clinical assessment . tmt - b is known to be a simple but effective tool for assessment 
 of cognitive abilities like executive function , visuo - conceptual function , visuo - motor 
 tracking and attention6 . betz and 
 fisher7 suggested that tmt - b be used as 
 a short test for predicting future traffic accidents or driving test failures and 
 occasionally in the evaluation of elderly drivers . many studies have regarded the tmt - b as 
 an easy and short test with ability to predict fitness to drive in the elderly or in 
 cognitively impaired drivers7,8,9 . these studies 
 reported significant association between drivers involvement in road traffic accidents and 
 their poor performance on the tmt - b . other studies have suggested that elderly drivers who 
 perform poorly on the tmt - b had a higher risk of involvement in traffic accidents9,10,11 . although the tmt - b test may be a simple 
 and useful measure of executive function as a predictor of an individual s fitness to drive , 
 it does not give a clear picture of the function and is not an easy test to administer . they also give a clear picture of the executive function and ensure uniform testing 
 conditions . we , therefore , developed a new test called the driving tmt - b ( dtmt - b ) that 
 presented a virtual environment in three - dimensional spaces to test the executive functions 
 of drivers . this study aimed to examine the validity of the dtmt - b as a predictor of an 
 individual s fitness to drive . thirty stroke patients ( right hemiplegia , 13 ; left hemiplegia , 17 ; age , 56.10 ,  9.40 , mean 
  standard deviation ) and 65 healthy control subjects ( age , 43.45  15.40 ) participated in 
 this study . the stroke participants sitting balance were normal and their brunstrom stage 
 of arm and hand were 2.8 ( sd=1.49 ) and 2.77 ( sd=1.52 ) , respectively ( table 1table 1.demographic characteristics of study participants and task completion 
 timesall(n=95)stroke patients(n=30)healthy participants(n=65)male , n ( % ) 53 ( 55.8)20 ( 66.7)33 ( 50.8)female , n ( % ) 42 ( 44.2)10 ( 33.3)32 ( 49.2)age ( years)47.44 ( 14.95)56.10 ( 9.40)43.45 ( 15.40)education ( years)13.57 ( 3.73)11.37 ( 4.00)14.58 ( 3.14)kmmse score28.17 ( 2.35)26.40 ( 3.21)28.98 ( 1.14)ctmt - b in seconds47.77 ( 3.55)85.80 ( 30.22)30.22 ( 13.83)mas1.60 ( 1.30)brunstrom stage ( arm)2.80 ( 1.49)brunstrom stage ( hand)2.77 ( 1.52)all values except gender are represented as mean ( standard deviation ) . kmmse : korean mini - mental status examination , ctmt - b : computerized trail making test 
 b ( sub - item of cpad ) , mas : modified ashworth scale ) . patients who ( 1 ) had visual neglect or apraxia , ( 2 ) had 
 limited range of motion , ( 3 ) had seizure or epilepsy , ( 4 ) could not sit unaided , ( 5 ) were 
 pregnant , ( 6 ) had psychiatric disease , or ( 7 ) had ataxia , were excluded from the study . kmmse : korean mini - mental status examination , ctmt - b : computerized trail making test 
 b ( sub - item of cpad ) , mas : modified ashworth scale all participants were provided a detailed description of the study and informed consent was 
 obtained from all patients prior to participation . human subject ethical approval was 
 obtained from the institutional review board of korea national rehabilitation center 
 ( nrcirb-2012 - 01 - 004 ) prior to conducting the study . participants were screened by using the korean mini - mental status examination ( kmmse)12 before enrollment . the computerized version of trail making test part b ( ctmt - b ) emulates the paper and pencil 
 version of the test on a computer screen . the cognitive perceptual assessment for driving 
 ( cpad ) developed by the korea national rehabilitation center has one such ctmt - b embedded as 
 a subtest . the cpad is a computer - based assessment tool to assess the driving capacity of 
 people with neurological deficits13 . the 
 ctmt - b presents 25 items including numbers and letters randomly scattered on an lcd screen . participants are required to click alternately on numbers and letters in numerical and 
 alphabetical order respectively . a total task completion time over 2 minutes was regarded as 
 failing the ctmt - b . according to park et al.13 , the subjects ctmt - b scores were associated with driving 
 performance such as car crash , vehicle positioning , and lane changes . traditionally , the tmt - b has been used as a measure of the executive function as well as of 
 processing speed and visual scan14 . the korean version of tmt - b15 was used 
 for the paper - and - pencil version of the test . the test required participants to connect a 
 set of numbers and letters positioned randomly on an 8.5 by 11 inch sheet of paper with 
 pencil lines . participants were asked to alternate between numbers and letters while 
 following numerical or alphabetical order respectively . primary end point of the test was 
 the time taken for completion of the task16 . during the test , errors made by the participants were pointed out 
 by the examiners and participants were redirected to the last correct selection and asked to 
 continue the task from that point . the stopwatch used to measure the performance time 
 continued even when participants made errors . a total task completion time exceeding 5 
 minutes was regarded as failing the tmt - b15 . dtmt - b is a driver screening assessment performed with a driving simulator incorporating a 
 modified version of the tmt - b . the simulator set up consists of a table , two led screens , a 
 small steering wheel , an accelerator and a brake . all subjects were explained the task 
 clearly and were allowed to perform in a practice session before the actual dtmt - b test . participants performed a simulated driving on a virtual road of 2,674  m presented on one led 
 screen , while a map showing a moving point indicating the current location as well as the 
 final destination were projected on the second led screen . the virtual roads were in effect 
 the tmt points and this task expected participants to drive along them rather than connect 
 them with lines as in the paper or computerized tmt . similar to the tmt - b , the dtmt - b 
 required connecting , that is , driving alternately through the locations marked by numbers 
 and letters in numerical and alphabetical order respectively . the driving speed was fixed at 
 40  km / h and was determined as optimal based on a pilot test conducted prior to the present 
 study . when participants made errors , the computer program indicated the error and relocated 
 the car to the last correct place . errors made by a participant reflected in their total 
 score as total task completion time . a total task completion time of over 15  min was 
 regarded as failing the dtmt - b ( fig . 1fig . 1.driving tools for driving trail making test - b ( dtmt - b ) ) . driving tools for driving trail making test - b ( dtmt - b ) the dependent measures were the times required to complete the ctmt - b , the tmt - b and the 
 dtmt - b respectively . for convergent validity , our study performed correlation analyses among 
 the dtmt - b , the kmmse , and the ctmt - b using the pearson s product correlation method . in the 
 validation study , intra - class correlation coefficients ( iccs ) were used for each task . iccs 
 values were graded as  poor to moderate  ( less than 0.75 ) good ( greater than 0.75 ) and 
  excellent  ( greater than 0.90)17 , 18 . thirty stroke patients ( right hemiplegia , 13 ; left hemiplegia , 17 ; age , 56.10  9.40  years ) 
 and 65 healthy control subjects ( age , 43.45  15.40  years ) participated in this study . the 
 stroke participants sitting balance were normal and their brunstrom stage of arm and hand 
 were 2.8 ( sd=1.49 ) and 2.77 ( sd=1.52 ) respectively ( table 1 ) . the stroke group s task completion time was significantly longer than 
 that of healthy participants ( table 2table 2.comparison between stroke patients and healthy participantsmeasuresstroke patientsmean ( sd)healthy participantmean ( sd)p valuetmt - b ( seconds)233.10 ( 83.12)108.38 ( 66.78)<0.001dtmt - b ( seconds)723.03 ( 246.38)416.25 ( 187.97)<0.001tmt - b : trail making test part b , dtmt - b : driving simulator running a modified version 
 of the tmt - b , p<0.001 ) . significant correlations were found between tmt - b and dtmt - b 
 ( table 3table 3.pearson correlation coefficients between tests ( n = 95)tmt - bctmt - bkmmsedtmt - b0.732 * 0.729*0.501*tmt - b : trail making test part b , ctmt - b : computerized trail making test b ( sub - item 
 of cpad ) , kmmse : korean mini - mental status examination , dtmt - b : driving simulator 
 running a modified version of the tmt - b . the icc values were 0.66 ( 95% ci = 0.4650.763 , p<0.001 ) 
 among all participants , 0.574 ( 95% ci=0.1060.797 , p=0.012 ) among stroke patients , and 0.499 
 ( 95% ci=0.1780.694 , p=0.003 ) among healthy controls ( table 4table 4.interclass correlation coefficients between tmt - b and dtmt - b across 
 groupsiccs95% confidence intervalslowerupperall participantstmt - b vs. dtmt - b0.6440.4650.763*stroke patientstmt - b vs. dtmt - b0.5740.1060.797*healthy controlstmt - b vs. dtmt - b0.4990.1780.694*tmt - b : trail making test part b , dtmt - b : driving simulator running a modified version 
 of the tmt - b , icc : interclass correlation coefficient , ci : confidence interval . * : p<0.05 ) . tmt - b : trail making test part b , dtmt - b : driving simulator running a modified version 
 of the tmt - b tmt - b : trail making test part b , ctmt - b : computerized trail making test b ( sub - item 
 of cpad ) , kmmse : korean mini - mental status examination , dtmt - b : driving simulator 
 running a modified version of the tmt - b . * p<0.001 tmt - b : trail making test part b , dtmt - b : driving simulator running a modified version 
 of the tmt - b , icc : interclass correlation coefficient , ci : confidence interval . * : p<0.05 this study found that the newly developed test dtmt - b test , which used a driving simulator , 
 was a reliable instrument for evaluating cognitive abilities like executive function . the 
 dtmt - b was demonstrated to be a good tool for evaluating cognitive abilities in a more 
 realistic environment of driving than done by other variations of the tmt - b test . many 
 researchers have used driving simulators in the assessment of driving performance in 
 individuals with various diseases and in elderly drivers because of the advantages offered 
 by them9 , 19,20,21 . moreover , many studies have found a correlation between driving 
 simulator training and improvement in driving skills22 , 23 . in one of these 
 studies , gamache , lavalliere , tremblay , 
 simoneau and teasdale reported a case study in which driving skills significantly improved 
 in a patient with total brain injury ( tbi ) after 1  year of simulator training . this study 
 also found an improvement in the patient s driving skills and safety in real driving 
 situations24 . the iccs between dtmt - b and tmt - b was reliable ( icc=0.644 ) . icc is defined as the 
 correlation between one measurement on a goal ( either a single rating or a mean of several 
 ratings ) and another measurement obtained on that goal . in our study the icc of all groups 
 was reliable though it was different between stroke patients and healthy participants 
 respectively ( icc = 0.574 , 0.499 ) . even though dtmt - b was not found to be a highly reliable 
 tool , the iccs between two groups were valid regarding the discrete discrepancy in their 
 cognitive abilities . the dtmt - b was more difficult to perform and complete than the tmt - b . however , it required the subjects to identify the route path in the 3 dimensional 
 environmental spaces , a task in which the executive function must be employed . wang et al.25 developed the rout map 
 recall test ( rmrt ) and validated it against the tmt - b . cronbach s alpha of the rmrt was 
 0.752 ( p<0.001 ) and its correlation with the chinese version of the tmt - b was 0.732 
 ( p<0.001 ) . though our study is similar in terms of using the tmt - b for testing participants memory , 
 attention , and executive function , we combined a driving simulator with the tmt - b . while 
 wang et al.25 used a 2-dimensional , 
 planar simulation , we used a simulated 3-dimensional space . driving simulator tests are safe as they avoid the risks associated with real driving , such 
 as traffic accidents . they also have higher face validity than pencil - and - paper tests , such 
 as the tmt - b26 , 27 . the use of a driving simulator also offers the possibility to 
 observe and evaluate clients driving abilities in a virtual reality version of real road 
 situations . a variety of studies have used driving simulators for evaluating and training 
 elderly or people with disabilities28,29,30,31 . this study analyzed the dtmt - b which combined a driving simulator with the tmt - b , and the 
 ctmt - b , a computerized version of the tmt - b , for the safe evaluation of drivers cognitive 
 functions . this study also analyzed the reliability of these tests by comparing scores 
 obtained in the paper version of the tmt - b . the tmt is a simple and short neuropsychological test that assesses cognitive abilities 
 such as visuo - conceptual and visuomotor tracking , sustained attention , and task alteration 
 ability6 . other researchers have 
 suggested that the tmt - b assesses processing speed , visual and motor integration , symbol 
 recognition and sequencing , executive function and in addition to other abilities7 . ricker and axelrod32 developed an oral version of the tmt ( otmt ) that had 
 significant correlation with the tmt - b ( r = 0.72 ) . in addition , messinis et al.33 reported that the color trail test had a 
 strong correlation with the greek tmt . correlations between dtmt - b and tmt - b , between dtmt - b and ctmt - b were very 
 strong ( r=0.732 , 0.729 respectively ) . this suggests that assessment of executive function 
 for fitness to drive recommendations could be evaluated using the simulator version of the 
 tmt - b . firstly , the small size of 30 stroke patients and 65 
 healthy participants is small and the results may not be representative of a larger 
 population . secondly , age and education level may have considerably influenced the subject 
 dtmt - b performance in the present study . the present study proved that the dtmt - b was effective as part of driver screening 
 assessment for stroke patients and healthy participants for assessment of cognitive 
 performance related to the executive function . this study was successful in developing the 
 dtmt - b as a 3-dimensional virtual environment to test the executive functions of drivers and 
 examined its validity . the 
 dtmt - b may be useful as part of driver screening assessment to assess the executive 
 functions of stroke patients as well as healthy people .
[ purpose ] the trail making test part b ( tmt - b ) is used in evaluating driving abilities 
 and includes testing for the executive function . a driving simulator version of this test 
 ( dtmt - b ) was developed to measure drivers executive abilities in three - dimensional space . 
 the purpose of the present study was to assess the validity of the dtmt - b for driving 
 assessment . 
 [ subjects ] thirty stroke patients and 65 healthy subjects were recruited . 
 [ methods ] participants performed the tmt - b and dtmt - b . 
 the dtmt - b was run on a driving 
 simulator in which the individual performed a task on virtual roads connecting the 
 lettered and numbered tmt - b points by simulated driving instead of connecting them with 
 lines as in the paper or computerized tmt - b . 
 intra - class correlation coefficients ( iccs ) 
 were used to assess validities . 
 significant correlations were found between the tmt - b and 
 dtmt - b . 
 [ results ] participants performed the tmt - b and dtmt - b . 
 intra - class correlation 
 coefficients ( iccs ) were used to assess validities . 
 significant correlations were found 
 between the tmt - b and dtmt - b . 
 [ conclusion ] the results suggest that the dtmt - b may be 
 useful as part of driver screening assessment using a driving simulator for stroke 
 patients and that it may also be used to assess the executive functions for healthy 
 people .