A spokesperson for Hampshire Police said at 11pm on Wednesday: "A motorcyclist has died following a serious road traffic collision on the A31 westbound near Ringwood shortly after 6.15pm on Wednesday, January 22.
"Two motorcyclists were in collision with a horse and came off their bikes.
"The men were taken by ambulance to hospital. One of the men has subsequently died of his injuries and the other is in a serious condition.
"The road is currently closed while police investigate the collision and diversions are in place.
"The circumstances of the collision and how the horse came to be on the road are under investigation.
"Anyone who witnessed the incident should contact Eastleigh Roads Policing Unit by calling 101."
The man's next of kin have been informed of his death.
The horse also died as a result of the collision.
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A Highways Agency spokesman said: “Our sympathies are with the family and friends of those involved in the incident that took place on the A31 near Ringwood last night.
“An investigation into the cause of the incident is being carried out by Hampshire Police and, as such, it would be inappropriate for the Highways Agency to comment on the cause.”
"As a result of a review of signage on the A31 between Picket Post and Ashley Heath near Ringwood, we are currently designing signs to enhance awareness and provide better information. We are on schedule to make these improvements by the end of 2014 at the latest."
Colin Draper, from the Verderers of the New Forest, the organisation that works to protect and administer the area’s agricultural communing practices, said police and agisters were investigating what happened.
“We now that there was a pony involved and it appears to have got onto the carriageway from the forest.
“We’re obviously very anxious to know how it got there, but at the moment we just don’t know.”
Desmond Swayne, MP for New Forest West, said: “I’m very concerned to hear that another person has died on that stretch of road and it must have been a ghastly experience for those stuck there.
“I hope that there’s a full analysis of exactly what happened.”
The incident took place on the westbound part of the dual carriageway, just half a mile from the Picket Post services.
At one time least a dozen emergency vehicles were seen heading the scene.
Hundreds of motorists are trapped on the major road as a result of the road closure.
Police officers were seen searching the undergrowth along the road as motorists got out of their cars whilst stuck in the gridlock.
The incident caused huge delays for motorists heading from Southampton on to Bournemouth, who were advised to find another route home.
There were also huge tailbacks across the New Forest getting into Lyndhurst at Emery Down.
The crash happened just after 6pm, an hour after the escaped horse had already brought traffic to a standstill.
Police earlier created a route through the debris caused by the crash between the two motorcycles and a horse in a bid to free the drivers who had been trapped on the A31 since 5.30pm.
The A31 was closed and the M27 was closed as far back at junction 2 to allow for better diversion routes for motorists.
Those trapped on the A31 were warned that the road would be closed for several more hours, fearing a long night stuck in their cars, but slowly motorists are being guided past the crash site.
A motorist, who has been stuck in his car for more than three hours, said: “Police have now created a route through the debris left by two motorcyclists that appeared to have crashed.
“Drivers are having to drive carefully through scattered parts of the bikes using both lanes, with police using flash lights to direct the traffic.
“The two bikes, one yellow and one red, are lying on their sides, on opposite sides of the road on the westbound side of the dual carriageway, with a great deal of small sections of the machines scattered everywhere.”
One motorist reported trapped cars were doing "U turns and going wrong way as no police instructions."
He added: "Accident clearly awful but @hantspolice making situ (situation) worse."
Vera Jardine said: "My daughter amongst lots of other travellers, has now been sat in the dark, no drink, no food, no facilities alone in her car for a total of 5 and a half hours so far and still has not moved.
"I realise the severity of the accident but surely something could have been done far earlier.
"Fortunately she is fit and healthy. I fear for the fragile and young in a similar dilemma.
"Just heard from her again. Still hasn't moved. First stopped about 5.45 pm."
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