Driver sleepiness contributes to a substantial proportion of all road crashes. Despite all that is known about driver sleepiness, bus drivers are often overlooked. What is certain is that bus drivers have the potential to suffer from sleepiness as they are shift workers. The current research used a large online survey to investigate sleepiness amongst London bus drivers. There were two aims; to quantify the prevalence of sleepiness amongst London bus drivers, and to determine the factors which contributed to sleepiness. Overall, 20.8% of respondents indicated that they had to fight sleepiness at least 2–3 times a week, and 36.6% of respondents stated that they had experienced a close call due to sleepiness in the past year. There were several potential causes of sleepiness including work, sleep, and personal factors such as obtaining less than 11 h rest between shifts, working 6 or more days without a rest day, and poor self-reported health. These findings show that sleepiness is common amongst London bus drivers and is caused by a combination of factors. The combination of contributory factors suggests that a multifaceted approach should be taken to reduce bus driver sleepiness.