A strike by train staff in the RMT union will severely affect rail services across Great Britain on Thursday, heralding the start of 10 days of transport disruption and delay around the peak summer holiday getaway weekend. About 20,000 RMT members at 14 train operators will strike for 24 hours on Thursday and again on Saturday, coinciding with the end of a week-long overtime ban by train drivers in the Aslef union. Both unions will also strike next week on the London Underground, all but wiping out tube services for most of the week and spelling heavy congestion on roads. Road congestion across the country will peak on Friday and Saturday, as most schools in England and Wales break up for summer. Cross-Channel ferry passengers have been warned of long queues at Dover. Some airport staff are also expected to strike the following weekend. Thursday’s train strikes will cut services across Great Britain’s rail network, with a number of cross-border services to Wales and Scotland cancelled even though the industrial action is only being taken at the English operators contracted by the Department for Transport. Most train operators will be running reduced timetables, although there are wide regional variations. The Rail Delivery Group, representing train operators, has advised passengers to check their travel arrangements in advance, with further cancellations and changes likely, including on the evenings before and mornings after all the planned strikes. A spokesperson said: “The upcoming rail strikes called by the RMT union and the overtime ban by Aslef will undoubtedly cause some disruption, affecting not only the daily commute of our passengers but also disrupting the plans of families during the summer holidays. “This will lead to disappointment, frustration, and financial strain for tens of thousands of people. We apologise for the inconvenience caused and understand the impact on individuals and businesses.” The effects of the industrial action will be compounded in places by engineering work, particularly on the main intercity route, the west coast mainline linking London to Glasgow via Birmingham, Liverpool and Manchester. Avanti West Coast will reduce to an hourly service while running no trains at all to north Wales, Blackpool, Stoke-on-Trent and Edinburgh. Other long-distance operators, including LNER and GWR, will make similar reductions, and TransPennine Express will cut some routes entirely. Northern has said it will run a “very limited” service. More than two-thirds of Southeastern stations will be closed, with South Western and Govia Thameslink Railway services also reduced. Commuter misery in the south will be compounded by London Underground strikes, which will stop virtually all services from Tuesday to Friday. The rolling action over six days from Sunday by RMT members – and Aslef drivers on Wednesday and Friday when some Unite staff will also strike – will also mean an early end to underground services on Sunday evening, with disruption on the mornings of Monday 24 July and Saturday 29 July. On the roads, the RAC and transport analysts Inrix are warning of particularly heavy traffic on Friday and Saturday, with 12.6m additional leisure trips over the first four days of most school holidays. The worst delays are expected to be on the M5 south-west of Bristol, which the RAC said would result in “bumper-to-bumper” traffic at peak periods. The Port of Dover warned that holidaymakers should expect to wait up to two and a half hours for border processing at the weekend because of additional post-Brexit passport checks, with 3,000 cars forecast to arrive for ferries early on Saturday morning. In better news for travellers, strikes planned at Gatwick by DHL ground staff for easyJet flights have been called off, although members of the Unite union working for other baggage handlers at the airport still plan action from the last weekend in July. A strike by Birmingham airport security staff has also been called off.