National is promising to connect Ōtaki to Wellington's electric commuter train network and fast-track a four-lane expressway from Ōtaki to Levin.
Party leader Judith Collins has announced National would invest $330 million in new transport projects for Horowhenua and the Kāpiti Coast if elected.
The projects include electrifying and double-tracking the rail line between Wellington and Ōtaki, building a full expressway interchange to Peka Peka, and completing the Horowhenua Expressway.
Collins said the projects would generate hundreds of jobs, reduce congestion, and bring the coast closer to Wellington.
The rail upgrades would allow people living in Manakau, Ōtaki and Te Horo to easily travel to Wellington, rather than relying on the once-a-day Capital Connection service from Palmerston North, Collins said.
"In time, we will look to electrify and double-track the line to Levin, expanding even further the pool of commuters able to use the service"
National's transport spokesperson Chris Bishop said the projects would help support major population growth.
New spending for these projects would be funded from National's proposed record $31 billion transport infrastructure plan.