Is there anyway to fast track building a city from scratch?

I am in the process of creating the map for my game concept. I have a map based on Houston, TX and it is similar sized. Real world sized and chopped up with the World Partition tool. I have essentially imported the OSM data and created a height map, I then properly scaled it in unreal to create a landscape terrain the size of Houston. The ground and everything else is fine. I then downloaded OSM data and made FBX files of all the railroads, roads, sidewalks, walking paths etc in the entire region of Houston(the part that I imported anyway). My question is, is there any possible way to convert the FBX!
files to a spline or have them form to the landscape to be useable as is? This is literally a city worth of landscape so it will take a super long time to create the splines manually. I am certainly not above doing this(already started), I just want to know if I can ease the pain on myself. I have uploaded a photo to illustrate what I am trying to portray. Capture.PNG|690x377
The green represents what I have manually splined so far. The orange is just the railroads only, as importing all the FBX paths at once will crash UE5 guaranteed. I hope to find a method and then I would create the roads, railroads, sidewalks etc all separately layered. It takes a while to pan the entire map even on 8 camera speed with the 100x modifier. Any help would be greatly appreciated. Please advise.