“There is overwhelming evidence that lower speeds result in fewer collisions and a reduced severity of injuries; and consistent evidence that casualties are reduced when 20mph limits are introduced.
“Mae tystiolaeth lethol bod cyflymderau is yn arwain at lai o wrthdrawiadau ac anafiadau llai difrifol; a thystiolaeth gyson bod gostyngiad yn nifer yr anafusion pan gyflwynir terfynau o 20mya.