Is Caffeine increase alertness?

Caffeine increased sleep latency (i.e., improved alertness) and auditory vigilance performance compared to placebo. 

Zwyghuizen-Doorenbos, A., Roehrs, T. A., Lipschutz, L., Timms, V., & Roth, T. (1990). Effects of caffeine on alertness. Psychopharmacology, 100(1), 36-39.