Functional near infrared spectroscopy (fNIRS) was used to measure drivers' brain activity while performing driving tasks on a driving simulator. Increased activation in the dorsolateral prefrontal region was observed when driving on a narrow road and when following a preceding vehicle compared with the level seen for ordinary driving. In addition, a difference in the level of activation attributable to the exercise of attention was seen between the different tasks of driving on a narrow road and ordinary stop-and-go driving.