This is reflected by actuaries when they set insurance rates for different age groups, partly based on their age, sex, and choice of vehicle. Older drivers with slower reactions might be expected to be involved in more collisions, but this has not been the case as they tend to drive less and, apparently, more cautiously. Attempts to impose traffic policies can be complicated by local circumstances and driver behavior. In 1969 Leeming warned that there is a balance to be struck when "improving" the safety of a road.Conversely, a location that does not look dangerous may have a high crash frequency. This is, in part, because if drivers perceive a location as hazardous, they take more care. Collisions may be more likely to happen when hazardous road or traffic conditions are not obvious at a glance, or where the conditions are too complicated for the limited human machine to perceive and react in the time and distance available. High incidence of crashes is not indicative of high injury risk. Crashes are common in areas of high vehicle congestion, but fatal crashes occur disproportionately on rural roads at night when traffic is relatively light. This phenomenon has been observed in risk compensation research, where the predicted reductions in collision rates have not occurred after legislative or technical changes. One study observed that the introduction of improved brakes resulted in more aggressive driving, and another argued that compulsory seat belt laws have not been accompanied by a clearly attributed fall in overall fatalities.
Cold sensitivity or cold intolerance is unusual discomfort felt by some people when in a cool environment.There is much variation in the sensitivity to cold experienced by different people, with some putting on many layers of clothing while others in the same environment feel comfortable in one layer.Cold sensitivity may be a symptom of hypothyroidism, anemia, fibromyalgia or vasoconstriction. Vitamin B12 deficiency usually accompanies cold intolerance as well. There are other conditions that may cause a cold intolerance, including low body weight, high body temperature and low blood pressure. There may also be differences in people in the expression of uncoupling proteins, thus affecting their amount of thermogenesis. Psychology may also play a factor in perceived temperature. See also
Apparent temperature
Thermoception
Raynaud syndrome


== References ==