The Transport Research Laboratory researched the causes of over 5,000 accidents. The data is shown below.
You can see that, contrary to popular belief, speed is not the primary cause of accidents. Indeed, excessive speed accounts for only 7.3%.
Sorry about the alignment!

Accident Cause Definite factors
Qty %
Failure to judge other persons path or speed 623 10.7%
Behaviour - careless/thoughtless/reckless 513 8.8%
Inattention 465 8.0%
Looked but did not see 436 7.5%
Excessive speed 424 7.3%
Lack of judgment of own path 369 6.3%
Failed to look 365 6.2%
Following too close 238 4.1%
Impairment — alcohol 222 3.8%
Slippery road 175 3.0%
Inexperience of driving 163 2.8%
Behaviour — in a hurry 157 2.7%
Site details — bend / winding road 131 2.2%
Surroundings — stationary or parked vehicle 112 1.9%
Crossed from behind parked vehicle, etc 105 1.8%
Surroundings — bend / winding road 104 1.8%
Behaviour — panic 91 1.6%
Aggressive driving 80 1.4%
Behaviour — nervous / uncertain 69 1.2%
Other — (personal) 64 1.1%
Impairment — illness 58 1.0%
Distraction — physical outside vehicle 57 1.0%
Surroundings — buildings, fences, vegetation 56 1.0%
Failed to see pedestrian or vehicle in blindspot 56 1.0%
View — glare from the sun 55 0.9%
Impairment — fatigue 48 0.8%
Weather (eg mist or sleet) 45 0.8%
Distraction — physical in/on vehicle 45 0.8%
Site details — narrow road 41 0.7%
Distraction — stress / emotional state of mind 39 0.7%
Inexperience of vehicle 37 0.6%
Surroundings — moving vehicle 31 0.5%
Animal out of control 29 0.5%
Site details — steep hill 28 0.5%
Other vehicle defects 26 0.4%
Tyres — deflation before impact 26 0.4%
Tyres — worn / insufficient tread 26 0.4%
Other (Local conditions) 24 0.4%
Site details — poor road surface 23 0.4%
Site details — roadworks 23 0.4%
Interaction or competition with other road users 23 0.4%
Defective brakes 22 0.4%
Site details — inadequate signing 17 0.3%
Impairment — drugs 17 0.3%
Ignored lights at crossing 15 0.3%
Person hit wore dark or inconspicuous clothing 15 0.3%
Disability 14 0.2%
Site details — poor / no street lighting 14 0.2%
Tyres — wrong pressure 9 0.2%
View — windows obscured 6 0.1%
High winds 6 0.1%
Defective lights or signals 5 0.1%
Earlier accident 4 0.1%
View — glare from headlights 1 0.0%
Number of factors reported 5847 100%