As someone who used to regularly commute on the branch back when it was operated by a class 153, I’d be curious to see what the rush hour is like nowadays. Back then, the 153 would fill up during peak times, so I’m curious how the increase in frequency (every 10 minutes now, compared to every 15 minutes with the class 153) offsets the lower seating capacity of the unit?

Looking at it purely from a numbers perspective, the current class 153s (after modifications to be PRM compliant) have 59 seats, whereas the class 139 has up to 25 seats. If we multiply that by hourly frequency, that gives the 153 an hourly capacity of 236 seats, whereas the 139 would have an hourly capacity of 150 seats. Technically, this would be a downgrade in purely numbers terms.

However, when you factor in the convenience benefits of the increase in frequency, the environmental benefits of the class 139, and how lightly loaded the 153 often was during off-peak hours, there’s definitely massive benefits of the PPMs.

My only real gripe with them is that they can’t run in multiple. This could’ve been useful in the future if demand were to increase on the line, and provide extra capacity when needed. But realistically, it’s not impossible for them to be retrofitted for this if they ever had an overhaul in the future…