Yesterday, we wanted to drive back from Yilan to Taipei only to notice that the HOV-restrictions there (minimum number of people per car > 3) seem to apply every Sunday (I previously thought those restrictions only exist on major holidays such as CNY/LNY).
The only information about this I found in English was a footnote in the over 10 year old 2012 National Freeway Annual Report:
Effective September 16, 2012, the HOV control was implemented regularly
between 14:00~20:00 hours on Sundays at the northbound entrances to the
interchanges at Toucheng, Yilan, Luodong and Suao. Results suggest that
the practice has effectively diverted the rush hour traffic (14:00~20:00) to
11:00~14:00 and 20:00~23:00, as average travel speed in the Hsuehshan
Tunnel during the hours grows from 40km/h to 55km/h and more. Average jam
at the entrances to the interchanges are reduced to about 500m and travel time
between the local roads before entering into the interchanges to the Nangang
System Interchange drops by more than 30 minutes
In Chinese, it was similar with mostly old news articles (> 10 years old) about this change coming into effect.
Apparently, this seems to be such common knowledge now so that the relevant agencies don’t even bother to inform about this fact… 
The real kicker: After we (involuntarily) spent some time in Yilan waiting for time to pass, we drove past an LED screen happily informing drivers that the congestion situation wasn’t that bad this day and that the HOV-restriction would end prematurely at 18:00… 
Is there any website to check those restrictions in real-time?
And especially to learn about if the restriction has been / will be lifted prematurely…?
