The spending is expected to ramp up from $3.4 billion next year to $4.4b a year by 2024/25.
For a Government that prides itself on its frugality and caution when spending money, it is much more aggressive with road investment.
But will we need all these motorways in 2065?
NZIER questions this, given the rapid development of new technologies for driverless cars, collision avoidance, assisted braking and car-to-car communication.
The rapid adoption of electric cars could also short-circuit the Government's big spending plans.
First, tests are already being done with "platooning" of cars that can drive closely together in lines in a managed way that reduces congestion.
There is also the potential for Uber-style services that allow car parking and car pooling in a way that reduces car and motorway use.
Secondly, these new technologies could bring better road safety through fewer collisions and accidents as predictive technologies help the driver brake, decelerate and swerve to avoid crashes.
Assisted braking and electronic stability control are just a taster of things to come.
New Zealand already spends $650 million a year making existing roads safer and promoting road safety.
These technologies are being more rapidly adopted than previous new technologies, raising the risk that by the time the motorways are fully built and paid for they way we use our cars will have changed dramatically.
Anyone watching the development and adoption of smartphones over the past seven years will realise how quickly the landscape could change.
The third spanner in the works for the heavy motorway spending is how it is currently funded.
Motorists pay a levy when they buy fuel, which is then redirected into road maintenance, new roads and road safety campaigns.
But the rapid adoption of more efficient hybrid and plug-in electric cars could blow a hole in that revenue base.
Surely it's time for the Government to take a lighter and cheaper approach that looks over the horizon at the coming benefits of new technologies.