Region: Wales
M4 in Wales
Statistics and options.
Section | Construction started | Opened to traffic |
| Newhouse-Coldra (J2(M48) to J24) | 1963 | August 1967 |
| Newport by-pass (J24 to J28) | Aug 1962 & April 1963 | May 1967 |
| Newport by-pass widening (J24 to J28) | May 1978 & April 1980 | April 1980 & Autumn 1981 |
| Tredegar Park-St Mellons (J28 to J29A(A48(M)) | November 1975 | October 1977 |
| Castleton-Coryton (J29 to J32) | October 1977 | July 1980 |
| Coryton-Miskin (J32 to J34) | September 1975 | December 1977 |
| Miskin-Pencoed (J34 to J35) | September 1975 | December 1977 |
| Bridgend Northern by-pass (J35 to E of J37(A48)) | October 1977, June 1978 & November 1978 | September 1981 |
| Pyle by-pass (E of J37(A48) to J39) | April 1975(I) | November 1977 |
| Port Talbot by-pass (J39 to J41) | February 1963 | July 1966 |
| Baglan-Briton Ferry (J41 to J42) | August 1992 | December 1994 |
| Briton Ferry-Earlswood (J42 to J43) | January 1992 | December 1994 |
| Earlswood-Lon Las (J43 to J44) | March 1990 | February 1993 |
| Morriston by-pass (J44 to J46) | August 1969 | 1972 |
| Pontardulais by-pass (J46 to J49) | August 1974 | April 1977 |