COMMUTERS are facing 18 days of closures on a major train route.

A “once-in-a-generation” upgrade is being carried out on the Brighton Main Line later this year and in 2019.

The line will be shut between Three Bridges and Brighton and Three Bridges and Lewes for a week at a time.

It will mean the 300,000 passengers who use the line every day will either have to use a bus or go on a longer, diverted route.

Commuter John Parker, 43, travels regularly from Worthing to London.

He said: “I appreciate the work needs to be done but this is going to cause a lot of disruption.

“I will probably try to work from home if I can but that is not always ideal.”

The closures run from October 20-28 this year and from February 16 to February 24 in 2019.

Network Rail and Govia Thameslink Railway say they have been deliberately planned for school half-terms.

This is when passenger numbers are lower and some people may be able to be more flexible with their travel plans or take holiday.

The work will focus on the Balcombe, Clayton, Patcham and Haywards Heath tunnels and the railway which runs through them.

Work to stem leaks into the tunnels and provide reliable drainage away from the tracks will also take place and signalling and power systems replaced or upgraded.

Network Rail managing director for the south east John Halsall said: “This is a long-overdue upgrade to one of the most unreliable parts of the south east’s rail network.

“Southern and Thameslink passengers deserve better and this work will help us deliver that for them.

“We know closing the railway will be unpopular and I’d like to assure passengers this decision has not been taken lightly.

“We explored a range of different options, but the only alternative to weekday closures would have required us to close this part of the line for 84 weekends.

“Clearly, that’s not acceptable to passengers or the region’s economy – but neither is doing nothing.”

Brighton Pavilion MP Caroline Lucas said: “Though major improvements are clearly needed on the line, I’m deeply concerned about the scale of disruption set to hit passengers.

“I’ve spoken to Network Rail about these plans - and urged them to keep disruption to a minimum.

“I’ve also demanded that passengers with season tickets are given a two week discount, and that those without season tickets are permitted to travel on replacement buses and alternative lines for free.”