Why is my transaction file growing when db is in simple mode and there are no waiting transactions

I noticed that my database log file has reached 160GBs. My database is in simple recovery mode and I used the following query to see if there are any waiting transactions.

SELECT d.name,d.log_reuse_wait,d.log_reuse_wait_desc
FROM sys.databases d

It returned log_reuse_wait 0 and description 'NOTHING'.
Why is my transaction log growing then?

Your file is probably large but empty.

In SSMS, right-click on your database and go into Tasks, Shrink Files. DO NOT HIT OK IN THIS DIALOG – but it’s the easiest way of seeing how empty your files are. Choose Log in the dropdown, and I imagine you’ll see that your log file is actually 99% empty.

You probably had a large process that grew the file to 160GB. You should probably shrink your file and then resize it to 160GB again manually (to reduce fragmentation), and then monitor how full it is using PerfMon counters.