Q&A: Could US-Canada border solve Irish dilemma?
Theresa May has said the government is looking at arrangements between the US and Canada as a possible solution to the Irish border issue. How close is the comparison?
What did the prime minister say?
Labour MP Emma Reynolds asked Theresa May to give an example of a border between two countries which are not in a customs union, but do not have checks on lorries crossing the frontier.
Mrs May said: "There are many examples of different arrangements for customs around the rest of the world.
"Indeed we are looking at those, including for example the border between the United States and Canada."
Is the US-Canada border a 'soft border'?
No. There is a significant amount of infrastructure at major crossings including checkpoints, areas for marshalling lorries and overhead gantries. Lorries are stopped at the border and there are immigration controls.
So it would not meet the UK commitment to avoid a 'hard border'?
No. The Irish government seems to have anticipated the Canada example. Taoiseach (Irish Prime Minister) Leo Varadkar visited the border last year.
He said it was "high tech and highly efficient, but make no mistake - it's a hard border".
He reiterated that position on Monday night saying: "That is definitely not a solution that we can possibly entertain."
Does it have any relevance to the Irish border?
It may be that the UK government believes that some of the technological and administrative arrangements used at the US-Canada border can help solve the problem in Ireland.
Brexit Secretary David Davis has also visited the border, specifically the crossing between Detroit and Windsor, which carries a lot of freight traffic between Ford car factories.
He spoke enthusiastically to the Exiting the EU Committee about the trusted trader scheme which operates on that border.
"I looked at the crossing times: 54 seconds. I looked at the mechanisms: easy, cheap, 15 years old," he said.
"I watched as drivers went through and had to hand over their ID cards, so they knew that they had never been involved in smuggling.
"Even in the most difficult environment, it worked very well."
Have there been any other feasibility trips to the US-Canada border?
The Commons International Trade Committee visited last month.
The pro-Brexit Conservative MP Marcus Fysh made an explicit link with the Irish border saying that the need for "hard" border gateways on the border itself is driven by immigration "which shouldn't be needed" if Ireland remains in a Common Travel Area.
He described it as a "very efficient border", where inspections can be done well back from border itself.
However, a fellow committee member, Labour MP Chris Leslie, drew very different conclusions from the trip.
"It's a hard border and would be devastating between Northern Ireland and the Republic," he said.
"More bureaucratic than Dover because each truck has to declare 26 different data elements for 40 different US agencies."
He described it as "staggering" that the prime minister should suggest the US-Canadian border arrangements could be a way forward for the border between Northern Ireland and the Republic of Ireland.