Increased train frequency in Auckland's Mt Albert could mean crossings will close for 45 minutes each hour during peak times.

That's on top of Auckland Transport's plans to put barrier arms and flashing lights on all city rail crossings over coming decades.

Many need to be done before the City Rail Link is completed, scheduled for 2025.

Auckland City Councillor Christine Fletcher says it's not good enough.

"The CRL will not work unless we invest in comprehensive-grade separation, because every 10-15 minutes, these trains are going to be coming along, and you're going to have the barriers down."

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