RESEARCH - 100 Car Naturalistic Study
The 100 Car Naturalistic Driving Study was conducted under the auspices of NHTSA. The study is described in this quote from the web site:
A key to the development of effective crash countermeasures is an understanding of pre-crash causal and contributing factors. This research effort was initiated to provide an unprecedented level of detail concerning driver performance, behavior, environment, driving context and other factors that were associated with critical incidents, near crashes and crashes for 100 drivers across a period of one year. A primary goal was to provide vital exposure and pre-crash data necessary for understanding causes of crashes, supporting the development and refinement of crash avoidance countermeasures, and estimating the potential of these countermeasures to reduce crashes and their consequences.
A similar study is currently being conducted in Canada by The Council of Deputy Ministers Responsible for Transportation and Highway Safety and is taking place in Saskatoon, Saskatchewan.
Update September 2021:
It appears that you have to register in order to access the data.
A similar study was also conducted in the US. Data from that study is also available.