A new terminal building resulting in the expansion of the road network was built at Pearson International Airport in Toronto, Canada. A laboratory study was carried out to assess the effectiveness of the proposed guide signs. Participants' decision times and the accuracy of the lane choices selected to reach a provided destination were measured as they responded to a sequence of road signs guiding them into and out of the airport presented on a desktop computer. The key results were as follows: participants showed high response accuracies and fast response times for signs for airport entry, the split between terminals, and the split between arrivals and departures; signs listing the airport terminals for nine airlines on each sign were associated with excessive response times; the split to parking at the arrivals–departures–parking decision point was misunderstood by one-third to one-half of drivers, who assumed that they could continue to the curbside, expecting to find parking there; and the current widely used car rental pictogram was poorly understood, and a new alternative design was preferred by participants.