That is the very short lived and now defunct "Start" track.
It was sold only for a few years in the early 2000s.
It is more rigid than the standard "Sport" track which makes it good for bridges. It is smoother than Sport as well (being hard plastic).
There is an adapter for Sport (the new standard track) to this but they have not been in production for a long time and can be hard to get.
Start only had 1 straight size and 1 curve radius so the layout options were limited.
You can sometimes find this track for sale online.
Keep an eye out on auction sites or try forums like slotracer.online or slotforum.com and ask if someone will sell you an adapter (I have seen adapters go for 30-40 GBP which is way too much).
Luckily the cars themselves are the same and fit on standard Sport track just fine.