I'm probably just stabbing in the dark with this one. Back in the early 80's back when I lived in Connecticut , I remember seeing MV tunnel lights unlike anything I remember . I got a decent look at one while we were sitting in stopped traffic in the tunnel . The fixtures were 400w MV with clear BT-37 lamps in various states of disrepair . What caught my attention was the fact that these lights didn't have a conventional socket . The lamps were mounted horizontally with spring clips retaining both the BT end and the base with another spring to contact the center contact of the base . Non of these had any form of refractor left that I remember and quite a few either didn't work or had missing lamps .

 Has anyone ever seen or heard of such a thing or is my memory just playing games with me .

 I believe the tunnel I remember is what's now called the "heroes tunnel" on the Wilbur Cross Parkway The current lighting appears to still be 180w SOX as of January of 2022 !  https://goo.gl/maps/SKihc52JLu77trHP8

They were still there as of August 2023!

 I don't know the status but I read that's there's been discussion of renovating the tunnel for a few years now.  I wish I could find photos of the original MV lighting ! It was nothing like I've ever seen before !

Funny you mention this tunnel, Tim!  I traversed through this very sad-looking SOX installation just last June.

My parents go through this area year and have for many years now, so I'll ask them. 

 Last time I was thru that tunnel , the sad looking lighting was the MV system ! Back then I lived near Westport CT .

LED now, anyone know the manufacturer?

That's honestly a real shame, but I guess it's to be expected with the discontinuation of mainstream SOX production back in 2019...