Mae ymchwil yn dangos y gallai'r terfyn cyflymder rhagosodedig o 20mya arbed £92miliwn y flwyddyn drwy leihau nifer y marwolaethau ac anafiadau. Gallai hefyd helpu i leihau'r pwysau ar y GIG yn sgil gostyngiad mewn anafiadau o ganlyniad i wrthdrawiadau traffig ar y ffyrdd.
Research shows the 20mph default speed limit could save £92m a year by reducing the number of deaths and injuries. It could also help to reduce pressure on the NHS from a reduction in injuries from road traffic collisions.