https://planning.hawaii.gov/wp-content/uploads/HART-presenta...
https://www.honolulutransit.org/inform/rail-facts#gsc.tab=0
*edit - decimal
Still, neither is something to take lightly (pun not intended), and I guess that building elevated makes construction a good chunk more expensive.
Here's the Hitachi Rail page with the trains, looks like four per car. http://italy.hitachirail.com/en/honolulu_381.html
So at 8 tons per axle its still within OP's truck limit.
Anyway I'm just kvetching because our 20-mile light rail is taking 22-years to build, is half complete, and a billion dollars over budget (as of now).