IIRC, "Reach the Beach" was a King WillieDon gig.
Replacing drawbridges on US 50 with continuous spans, widening the roadway, etc.
But, that wouldn't necessarily explain non-mainline improvements.
Willie Don figured out what was good for MD was good for Baltimore ... if money came into MD, there was money to share with The City, because the MD Constitution according to LawGiver Goldstein was that MD may not go into debt to gift money to the city. (I don't actually know if Willie Don figured it out or if Uncle Louie just told him point blank one day.)
This was decades after the State Roads thing ... almost at or maybe even at the end of it.
The mainline and non-mainline improvement stuff during Willie Don's reign were from his understanding of tourism ... make the roads nice and signage easy to see and understand and tourists will recommend it. It worked; tourist came and left their money, told others to do likewise.
Glendenning killed it and future funding of the idea.