Four of the top ten most dangerous council-managed A-roads in England are in Lancashire
Among the 10 stretches of road expected to see the greatest casualty reduction include the A588 between Lancaster and Skippool, Lancashire; the A4 between Junctions 5 and 7 of the M4 in Slough, Berkshire; and the A631 between Market Rasen and Louth in Lincolnshire.
The analysis by the Road Safety Foundation and the RAC Foundation found that the safety improvement will be worth £550 million.
They described the £100 million work programme as unique because it aims to reduce risk through a proactive approach which is already applied in areas such as medicine, mining and aviation.
Rather than the traditional method of improving safety after a crash has occurred, the scheme uses road engineering to try to prevent crashes from happening in the first place and making roads more forgiving when accidents occur.
Some of the 48 projects involve simple measures such as installing rumble strips, improving visibility at junctions and removing trees, poles and lighting columns.
The investment comes from the Safer Roads Fund, created by the Department for Transport.
RAC Foundation director Steve Gooding said the programme will "re-engineer and rehabilitate some of the riskiest roads we have".
Road Safety Foundation executive director Dr Suzy Charman said: "Finding the right funding mechanisms for safety improvements to our road infrastructure is absolutely essential if we are to break the current plateau in the number of people being killed on our roads.
"The Safer Roads Fund has given us a truly innovative approach to tackling risky roads."
The number of people killed on Britain's roads in 2017 was 1,793.
This was one more than in 2016 and only fractionally lower than the 2010-14 average of 1,799.
- Here are the 10 stretches of road expected to see the greatest casualty reductions, including the county where the longest part of the link is and the estimated fatal and serious injuries prevented over 20 years:
1. A588 between Lancaster and Skippool, Lancashire 151
2. A683 between Lancaster and Kirkby Lonsdale, Lancashire 114
3. A18 between Laceby and Ludborough, Lincolnshire 91
4. A529 between Hinstock and Audlem, Shropshire 68
5. A5012 between Newhaven and Cromford, Derbyshire 58
6. A684 between Leeming and Sedbergh, North Yorkshire 55
7. A4 between Junctions 5 and 7 of the M4 in Slough, Berkshire 54
8. A6 between Lancaster and Junction 33 of the M6, Lancashire 47
9. A361 between Banbury and Chipping Norton, Oxfordshire 46
10.= A581 between Rufford and Euxton, Lancashire 43
10.= A631 between Market Rasen and Louth, Lincolnshire 43