As advanced electronic technology continues to be integrated into in-vehicle and portable devices, it is important to understand how drivers handle multitasking in order to maintain safe driving while reducing driver distraction. NHTSA has made driver distraction mitigation a major initiative. Currently, several types of Detection Response Tasks (DRTs) for assessing selective attention by detecting and responding to visual or tactile events while driving have been under development by an ISO WG8 DRT group. Among these DRTs, the tactile version (TDRT) is considered as a sensitive surrogate measure for driver attention without visual-manual interference in driving, according to the ISO DRT Draft Standard. In our previous study of cognitive demand, our results showed that the TDRT is the only surrogate DRT task with an acute sensitivity to a cognitive demand increase in an auditory-vocal task (i.e., n-Back verbal working memory task). At the same time, a specificity for responding to only increased cognitive demand, not to increased physical demand for a visual-manual task (i.e., Surrogate Reference Task or SuRT). Similar findings in both simulated and on-road driving confirmed that the TDRT is a sensitive, specific and reliable surrogate test for measuring the effects of secondary tasks on driver attention. The current paper further investigated eye glance patterns and subjective ratings, and their relationship with DRT metrics, allowing a more comprehensive understanding of the attentional effect of secondary tasks on driver performance.