I'm not against either idea per se, but it seems to me that investment in better PT and cycling infra and otherwise encouraging people who are able to use it as an alternative to their car is the more efficient and future proof solution to reducing congestion. More car lanes just makes the place less liveable, and too often it just moves the choke point instead of eliminating it.
It sounds to me like National is just doing its typical conservative "we'll do everything like the 1950s because it worked for white men and appeals to egotists" spiel again.