There are several potential benefits to the concept of so-called “truck platooning.” The truck in front reduces air resistance for those behind it, which may reduce emissions and boost fuel economy. There may be benefits in terms of traffic flow and capacity, too.

However, there are also clear concerns about safety, given the technology’s nascent nature. The U.K. government commissioned a feasibility study back in 2014, which recommended conducting trials.

Those trials were announced Friday. They will be led by the British Transport Research Laboratory (TRL), and consortium members participating in the trial will include the Dutch truck-maker DAF (owned by the U.S. firm Paccar), British engineering consultancy Ricardo, and German logistics giant DHL. The trucks will have humans in them at this stage, even if they’re not actively driving at all times.

In a statement, TRL said the trial would draw on experiences from similar tests in Europe and the U.S.—officials from states such as California, New Mexico, Arizona and Texas are currently working to coordinate their regulations for tests.

So why have the British trials taken so long to happen—especially since the feasibility study took place in 2014? It’s partly due to the government’s previous failure to find a truck manufacturer to take part. It also may have something to do with disagreements over where the tests will take place.

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“We all want to promote fuel efficiency and reduce congestion, but we are not yet convinced that lorry [or truck] platooning on U.K. motorways is the way to go about it. We have some of the busiest motorways in Europe with many more exits and entries,” Edmund King, the president of the AA (formerly known as the Automobile Association), told The Guardian. “Platooning may work on the miles of deserted freeways in Arizona or Nevada but this is not America,”

King suggested that a platoon of three trucks—the maximum envisaged for the upcoming trials—could obscure road signs from other drivers and make life difficult for those who want to enter or exit the motorway.

“Obviously it’s important to get this right,” a spokesperson for the transport department told Fortune. “The trials are going to take place not on a road initially. The AA et cetera have come out today and talked about concerns for safety. The reason we’ve done it this way is to allay those concerns.”

According to the department, the initial test track trials—for which there is not yet a firm date—will be followed by tests on actual roads by the end of next year. “Each phase of the testing will only begin when there is robust evidence that it can be done safely,” the department said in a statement.