Ireland has 208 Border crossings, according to the first officially agreed count since the island was partitioned, almost a century ago.

Emails between Government technicians reveal they endured a “nightmare” trying to definitively map out all roads, paths and dirt tracks that traverse the 500km frontier. In addition to technical limitations, there was confusion about crossings where the Border runs up the middle of roads or juts in and out of routes, or where roads are privately owned on one side and publicly maintained on the other.

The joint mapping exercise involving the Department of Transport and the Northern Ireland Department for Infrastructure, which started last year, came to light after being referred to in minutes released after a Freedom of Information request.

On one section of the Dublin to Belfast motorway, traffic travelling in one direction is in the North while that travelling in the opposite direction is in the South, the documents also reveal. It is “half north and half south”, an official says.

Previous estimates put the number of road crossings between Ireland and Northern Ireland – the UK’s only land border with another European Union country – at 275. In one of the final emails between Dublin and Belfast in recent weeks, signing off on the first agreed count, an official concludes: “I’m now getting 208 Border crossings in total, hope you are too.” The final figure will confirm there are more crossings in Ireland than along the entire border between the European Union and the countries to its east, which has 137.

The emails show officials immediately ran into difficulties when they began working together, last November, over differing classifications between Belfast and Dublin of whether roads were public or private. “It’s almost impossible . . . due to the variation in this on each side,” said one.

Another official conceded the final report on Border crossings may have to carry a disclaimer. “With something so ambiguous as the Border there will be a few metres out here and there,” he said.

A third added: “There are practical implications when it comes to roads that are split along the middle that probably can’t be represented on maps; but that is as good a way of representing it.”