Van Vleuten takes second, with Longo Borghini in third
That was a tough sprint. The Dutchwoman sandbagged Longo Borghini all the way to the final straight and then came up the insider of her in the last 50m.
Vos won the small kick for fourth to underscore an epic day for Dutch road cycling.
Anna van der Breggen is the double world champion...
She crosses the line with plenty of time to drink in this astonishing and dominant victory. She gives a little thumbs up before crossing the line arms aloft.
2km to go – Longo Borghini & van Vleuten onto the circuit
They will fight it out for the silver medal. You would back the Italian in normal circumstances, but who knows who has the most in the tank remaining.
5km to go – Uttrup Ludwig not done yet
The Danish rider has attacked out of the pursuing group and is powering ahead. She's in fourth place on the road.
Anna van der Breggen is not far from the finishing straight now.
9km to go – Powerful chase duo
It's Longo Borghini and van Vleuten who are battling on for the silver and bronze. This pair left the other favourites towards the top of the final climb, and there's a lot of daylight between them and the next group already.
10km to go – One last time up the Gallisterna
Van der Breggen has crested the climb and she'll enjoy this final closing 10 kilometres to the Imola race track.
Some very weary legs out there now. It's Uttrup Ludwig first to try her hand and she takes Longo Borghini with her in the slipstream. Deignan is not far behind and there behind, as always, is van Vleuten.
15km – Silver for the peloton
With one more climb remaining, the peloton is now thinking about how to win silver, rather than how to stop van der Breggen getting gold.
The Dutchwoman's lead is 2'20" and she is uncatchable.
20km to go – Italy is nice
The kilometres are ticking down, with just 20km remaining for our lone leader Anna van der Breggen. She's showing so sign of slowing down at the moment as she draws on the skills that won her the individual time trial just two days ago. It's going to be double rainbows for the Dutch.
The Coach weighs in
25km to go – It's looking good for the Dutch
The time gaps is 1'40" and Italy are gritting their teeth in an attempt to bring the chances of victory back for the home nation.
27km to go – Chasers pack it in
Not something you see terribly often, but possibly this is a sound tactical move.
The four riders pursuing van der Breggen have knocked off their efforts in the hope that they can use the strength of what remains of the peloton to help them in bringing her back. Deignan and Longo Borghini can now draw on the strengths of their domestiques, as well as bringing a few more of the favourites – notably, Niewadoma – into the chase effort.
32km to go – Is this the race-winning move?
Anna van der Breggen now was a full minute of advantage over the chasing group. She's pulling out her lead more and more, while Deignan, Longo Borghini and Uttrup Ludwig struggle to contain her.
Even if they do catch up, they will have to contend with a fresh Annemiek van Vleuten at the finish, who is having an armchair ride right now.
37km to go – Dutchies go over the top
That powerful work from van Vleuten paved the way perfectly for a counter attack from Anna van der Breggen. She blasted clear as son as van Vleuten eased up, and now has 30 seconds on the chasing trio of Deignan, Longo Borghini and Uttrup Ludwig, with van Vleuten sitting in as a passenger.
41km to go – Vos still the boss
And just like that it's over. An injection of pace from Marianne Vos makes mincemeat of the gap and all of a sudden it's gruppo compacto on the penultimate climb of the Gallisterna.
Annemiek van Vleuten takes up the cudgel after her countrywoman and she has dragged a very elite group clear. Elisa Longo Borghini is there, Cecilie Uttrup Ludwig and Anna van der Breggen are in her wheel, with Lizzie Deignan a few bike lengths off the back with Lianne Lippert.
42km to go – Bujak back on the attack
There are four Dutch riders still on the front of the peloton and the gap is down from two-and-a-half minutes to a paltry 18 seconds. The peloton does not look to be much more than 40 riders, now.
Slovenian rider Eugenia Bujak is not happy to be caught up by the peloton after expending all that energy to get over to the break and she is now forging on once more.
48km to go – Favourites to the fore
As soon as the peloton reached the lower slopes of the Mazzolano they started chasing and almost instantly the gap to the break evaporated.
Deignan (GBR), van der Breggen (NED) and Longo Borghini (ITA) are all prominently placed at the front now and they're devouring what's left of the gap. Bujak has made the junction with the break.
50km to go – Riders getting shelled
As Australia continue to work with the Netherlands on the front of the bunch, we're seeing the gap to the breakaway fall for the first time since Tayler Wiles led them up the road.
The time gaps are 1'25" to the peloton and 31" to the chasing Eugenia Bujak from Slovenia.
The new impetus has forced a lot of riders out of the back and we've just seen a crash for Ashleigh Moolman-Pasio on the tortuous twisting descent off the Bergullo. Let's hope the South African can regain contact at this crucial point in the race.
54km to go – Tiffany Cromwell pulls the bunch
The Aussie was a late callup to this race after her compatriot Amanda Spratt was ruled out with concussion. The gap now stands at 2'20" and Eugenia Bujak is somewhere floundering in the middle of that.
They are headed onto the penultimate lap of the circuit now, as any remaining domestiques grab feed bags for their leaders.
A fine summary
And while we have a lull, here's a little plug...
There are no West African riders in the peloton today, nor will there be any in the men's race tomorrow. The Lunsar Cycling Team is a grassroots club in Sierra Leone, focused on developing the sport in their country and giving riders from the tiny nation a chance to compete on the international stage. The first step to that goal is getting some decent bikes, which they are currently fundraising for on GoFundMe.
65km to go – Attack de Bujak
Slowly the peloton is being whittled down. There's very little chance to come back on this course so once you're dropped, you're going to stay dropped.
Meanwhile, Eugenia Bujak of Slovenia has had a dig and she's relying on her TT skills to help her cross the gap.
It feels like a bit of a lull again after that flurry of attacks earlier. Nobody in the peloton seems interested in chasing.
68km to go – Spotted!
That's our first sighting of Annemiek van Vleuten since the neutralised rollout. She's come straight to the front, as have Elisa Longo Borghini and Kasia Niewadoma.
71km to go – Doebel-Hickok attacks again
The American has another dig off the front, but she can't quite force a gap. She won't want to pull the peloton across the gap what with her team mate Wiles being in the lead group. It's been an eventful day for Doebel-Hickok, she's attacked twice and had to chase on after a mechanical.
The gap to the leading group has ballooned up to 1'30", which is great news for the leaders as they take on the final punishing inclines of the Gallisterna.
78km to go – Alice Barnes dropped from break
Hannah Barnes remains in place, while Tayler Wiles is absolutely grinding on the front to keep this escape away.
Grace Brown also seems to have lost contact on the really steep part of the Gallisterna. The gap is 18 seconds.
80km to go – third passage of the Gallisterna
Well this deluxe move has really put the cat among the pigeons. It's Spain who are having to do the chasing as one of the biggest teams to have missed the move.
Great Britain's Lizzie Deignan will also be delighted with this composition. She has two team-mates in the leading group.
Mavi Garcia lights it up now! The Spaniard has been on fantastic form and she's crossed the small gap between bunch and break in a few moments.
83km to go – Grace Brown kicks it all off
A counter attack from the Aussie sees her link up with Alison Jackson of Canada to make it a lead duo. They have a small gap to the peloton.
Tayler Wiles of Team USA has also launched a chase effort, bringing another seven or eight riders, including both Alice and Hannah Barnes from Team GB across with her. For the first time we have a leading group that could make life difficult for the peloton behind. Amy Pieters (NED) Juliet Labous (FRA), Christine Majerus (LUX) and Lisa Brennauer (GER) are all involved.
It's Russia and Italy now leading the chase from the peloton.
88km to go – It's all about saving energy
We have an attack off the front from Canada and it's being followed by a pair of riders including Cuba's Arlenis Sierra. This is an attempt to make something happen just short of the halfway point in the race. The wisest course, however, is sometimes to do nothing.
While it might be fair to suggest it has been a slightly slow start to the racing action today, there's no disputing the beauty of the Italian countryside...
Valerie Demey is being left to dangle off the front of the race as she crests the Gallisterna with a 'gap' of 6 seconds. The peloton are just awkwardly trying to ignore her, like someone they once went on a Tinder date with and have spotted on the train.
With a mere 100km remaining, it's about time for a patented van Vleuten hulk smash.
100km to go – Chase group formed
Some of the dropped riders from the peloton have formed a group of about 10 chasing back onto the peloton. It's going to be a long and brutal day for them.
The leader, Demey, is about to begin the Gallisterna and has 22 seconds advantage on the pack.
107km to go – Attack from Valerie Demey
The Belgian rider just clipped off the front there and nobody reacted. Remarkably, this is the first attack we've seen get any sort of gap on the peloton and we're over 35km in.
She has just crossed the summit of the Mazzolano climb with a 30 second gap.
It's notable at the front of the bunch that neither Italy or Netherlands are putting riders on the front. They're content, it seems, to let this move go.
111km to go – Mechanical issue for Krista Doebel-Hickok
The US rider who plies her trade for Rally Cycling, the second tier ProTeam, has had a small issue with her bike. She has been on good form since the season restart and earned herself a first ever Worlds call-up this season after an impressive podium result in the climbing heavy Tour de L'Ardeche in France earlier this month.
Let's hope there's enough road left for her to regain contact. At the moment, the lead riders aren't really hammering it on the front.
118km to go – Crash! Four laps remaining.
This course is going to create chaos today. There has been another crash at the back of the peloton with Anna van der Breggen of the Netherleands, Canadian rider Magdeleine Vallieres and a couple of others involved. There's really nowhere to rest or recover or regroup, and so those riders at the back are having to take extra risks, make extra efforts and generally fight harder to stay in touch.
Van der Breggen is back on her bike right away and chasing back, but she really did not need to have this extra bit of stress to contend with at the end of lap 1.
127km to go – Over the Gallisterna
The peloton heads over the summit of this cruelly steep climb for the first of five times. The full climb averages just 6.4% but the middle chunk is a ferocious 10.9% gradient with a peak of 14%.
We are already seeing riders being shaken loose by the cruel gradients, with Ann-Sophie Duyck and Fien van Eynde of Belgium both losing contact. It'll be a big blow for that nation's hopes to lose two helpers on the first lap. They're battling hard and might be able to catch back on the descent.
130km to go – Team dynamics
We've talked a lot about the Dutch team, but there are other strong outfits in this race. Italy as hosts are allowed to bring a full complement of riders with Elisa Longo Borghini their strongest performer at the moment. Longo Borghini took a stage win at the Giro Rosa earlier this month and is one of the favourites today.
Also bringing a full seven riders are Australia and Germany, with the USA down to six after losing Chloe Dygert to an horrendous crash in the individual time trial a couple of days ago.
Watch: Dygert’s horror crash at World Championships
And all this is to say nothing of Team GB, who come into this race with better form and a stronger team than we've seen in several years. Lizzie Deignan leads the squad, bringing some excellent form into the race after back-to-back wins in GP Plouay and La Course. She's backed by the Barnes sisters, Alice and Hannah, as well as the powerhouse Lizzy Banks (stage victor in the Giro Rosa and runner up to Deignan at Plouay). Completing the six-woman squad are Anna Henderson and Anna Shackley.
136km to go – First sight of the descent off Bergullo
And it's an extremely technical one. The road twists and turns back on itself in a really sinuous fashion and we could see that create some problems later on.
The advantage in descents like that is always with a lone rider versus a peloton, particularly towards the back of any groups where any changes of speed are magnified. That would suit an attacking soloist like Annemiek van Vleuten, or a fearless descender like Kasia Niewadoma.
The next climb is the Mazzolano and it's brutally steep. On this first passage it seems as though the bunch are taking it easy.
141km to go – Another crash!
Gosh this is nervous stuff. The flag dropped and the pace immediately increased.
An Ethiopian rider came down at the back of the peloton this time and another rider falls off the edge of the road and ends up on the grassy verge.
We are already climbing and the pace set at the front is creating early casualties.
And they're not even out of the neutral yet. The race was intentionally slowed by the commissaires at the front and as a result a concertina effect has caused a small pile-up. Unfortunately for British fans, Lizzy Banks, one of the in-form climbers in the women's peloton is one of those caught up. She's going to need a bike change.
This holdup means the 'neutralised' part of the race has been extended and we may actually see them start to climb the first ascent of the day still under the neutralisation.
143km to go – And we're off!
The peloton has rolled over the start line on the Imola race track and they are rolling along waiting for the flag to drop. The climbing on this course kicks off pretty much immediately, so it'll be fascinating to see who – if anyone – can make it into a breakaway.
So, a bit more on the Dutch. They've won the rainbow bands for the last three World Championships, with Annemiek van Vleuten the current defending champ. Two years ago it was Anna van der Breggen who took gold, and the year before that it was Chantal Blaak. All three of them will start today, along with Marianne Vos, Demi Vollering, Amy Pieters, Ellen van Dijk and Fllortje Mackaij. It is an astonishingly strong team, capable of winning on any sort of course.
Also, it's rare among some of the starrier national squads for riders used to being the outright leader on their trade teams to work selflessly for each other's interests. Not so with The Netherlands. They've shown a frightening ability in recent years to pull together for the good of the team, which should have some of the other squads feeling very nervous.
The 2020 World Championships had been scheduled to be held in Switzerland, but a Swiss government extension of Covid-19 quarantine restrictions forced the UCI into a late venue change, moving the event to Imola in Italy.
As well as a venue change there was also a change in schedule, with the two individual time trials moved and the junior and U23 events postponed for a year, meaning that the 2020 Worlds will consist of four races across four days from Thursday 24 September to Sunday 24 September. Today is day three and the first road race.
Yesterday saw the home rider Filippo Ganna take gold in the men's elite ITT.
'A supersonic effort!' - Ganna powers to world title
There are 145 riders set to compete over a hilly 143km, five-lap course. There are two key climbs that will define the race, but neither is truly monstrous. They're short and stabby, with the Cima Gallisterna looking the more likely to prove decisive.
And welcome to Imola where we're just about underway with the women's elite road race. The winner today will be entitled to pull on the fabled rainbow bands for the following year's racing and write her name in the history books of this fine sport.
The big question today is whether the Dutch domination of the World Championships will come to an end.