Original sentence: At 229 km, it  is considered the “spinal cord” of Sardinia.It has a lenght of 144 km.The infrastructure was modernized under fascism, and in the 1970's was rebuilt, becoming a Superstrada (Dual carriageway), however it is still a second category extra-urban road, and the speed limit is 90 km/h
Edited sentence: At 229 km, it  is considered the “spinal cord” of Sardinia.It has a length of 144 km.The infrastructure was modernized under fascism, and in the 1970s was rebuilt, becoming a Superstrada (Dual carriageway), however it is still a second category extra-urban road, and the speed limit is 90 km/h