If I'm reading this correctly, Lower Base Line just east of Tremaine will be closed for two years due CN construction.
https://www.miltonnow.ca/2023/06/30/112465/
Yup.
2km detour north to Britannia.
If signage is correct, after 2 years Lower Base is now open past Tremaine
Lower Base line is opened since last month. Beautiful!
Watch for occasional works (electrical) during working hours.