Motorists are being warned to allow plenty of extra time for journeys this weekend as strike action is expected to drive people towards their cars in huge numbers and disrupt the weekend plans of millions of people.

Tomorrow's third national rail strike of the week is set to clash with the travel arrangements of thousands of people attending big events in both Kent and London – while the A249 is also scheduled for another round of weekend road closures.

In Kent, Armed Forces Day celebrations in Medway, Mote Park's first Foodies festival being headlined by East 17, Scouting for Girls and Lee Ryan and Simon Webbe from Blue, Canterbury student event We:Connect and the city's Wine Festival are among the major events taking place.

Hundreds of families are expected at the 13th Armed Forces Day celebration in Gillingham, between 11am and 5pm, on Saturday at The Great Lines Heritage Park. A military parade, fun fair, concerts, children's activities and displays are all planned for the day hosted by Medway Council in conjunction with the Royal School of Military Engineering.

To help people reach the venue, shuttle buses are running from both Chatham Waterfront and Gillingham's King Street while a park and ride service between Chatham Dockyard's car park and Great Lines will run every 15 minutes transporting visitors coming by car for just £1 - while under 16s, serving military personnel and retired veterans can climb aboard for free.

National Highways says it expects motorways and major A-roads to be busier than usual because of the disruption happening on large parts of the rail network, which is affecting services on both designated strike days and the mornings and evenings either side as safety checks are completed and trains shuffled back into position.

And as work continues on the M2 junction 5 improvement scheme, the A249 between Sittingbourne and Stockbury faces another series of weekend closures and diversions for drivers.

Despite abandoning one overnight closure this week, road chiefs say all other road works are going ahead, which will mean lane closures on the A249 on Friday night and the complete closure of the southbound carriageway during the day on both Saturday and Sunday, between Bobbing and the Stockbury roundabout, for drivers trying to reach Maidstone.

Concerts by Ed Sheeran at Wembley Stadium and performances by Elton John and The Rolling Stones in Hyde Park and the theatre showcase West End Live, which attracts 500,000 people over two days, are among the big events happening in London over the coming days.

But despite Kent's close proximity to the capital, Saturday's rail strike is forcing ticket holders to explore alternative options for getting to the gigs.

The first rail trike on Tuesday saw about 20% of services to London running, hundreds of stations closed and most trains stopping by 6pm.

Data from satnav firm TomTom showed that congestion levels in the capital were also up 26% compared to previous Tuesdays, while people in cars or buses between 6am and 10am needed 72% more time to complete their journey with travel times almost doubling across London between 8am and 9am.

Musician Ed Sheeran is playing Wembley Stadium tonight and tomorrow. But Saturday's strike, combined with warnings of a reduced tube timetable and a 'check before you travel' warning for evening services on the Jubilee, Central and Victoria lines because of further industrial action, has left people fighting for parking spaces near the venue with others complaining the situation has forced them to give up their tickets altogether.

Ticket holders have taken to social media in their droves to complain about a shortage of parking options and hotel rooms caused by the strikes - among them Sheerness dad Garry Ratcliffe who said prices have been pushed so high that he was offered £405 for a car parking space that would enable him take his disabled son to the concert.

But after putting out a desperate plea on Twitter for help or options to get his 18-year-old son, who has cerebral palsy, to the show, which had thousands of re-tweets including one from Judge Rinder, the family have now been offered a staff parking space at the venue.

To try and minimise the potential for weekend disruption National Highways, which operates and maintains 4,300 miles of roads, says it is poised to call on more traffic officers and control room staff to manage the extra congestion - with officials also looking at putting recovery crews close to motorways on key routes to clear incidents quickly when they occur to prevent long delays building.

Mel Clarke from National Highways, said drivers can also do their bit by making sure their cars are roadworthy, have petrol and are without faults before setting off this weekend.

She added: "National Highways will be putting measures in place to ensure we continue to keep the country moving safely and deal with any increased traffic volumes caused by rail strike action.

"Roads could be busier than usual during strike days so we’d recommend that drivers plan journeys in advance and carry out basic checks to make sure vehicles are roadworthy. This includes checking tyres, engine oil, water, lights and ensuring you have enough fuel to get to your destination."