Contractors for the controversial HS2 will start tunnelling through the Chilterns next year – but project bosses say it is still “too early” to say what effect it will have on traffic in Bucks, to the frustration of residents.

The 15.8km long Chiltern Tunnel – which will start just inside the M25 south of junction 17 and come out northwest of South Heath – will start to be constructed in late 2019, with two tunnelling machines, each two football pitches long, doing the digging.

The different construction companies involved in the Chilterns section of the contentious high speed line met with residents in Amersham on Monday to reveal the latest details of the work they will be carrying out – including building a new haul road and making “highway improvements” to a main road in Great Missenden.

The new haul road – which will only be used by HS2 construction traffic to transport materials – is set to connect the A413 Great Missenden roundabout to the north portal of the Chiltern Tunnel in a bid to keep HGVs off the smaller country roads.

The two roundabouts on the A413 that connect Link Road from Great Missenden, Frith Hill and A413 to Amersham will be redesigned with lane widening to make space for both general and construction traffic.

Dozens of residents raised their concerns about the project, with one demanding HS2 bosses start giving residents facts and “stop procrastinating” about revealing the impact the works will have on traffic and congestion.

He said: “Whilst you’ve said you’re working very hard to reduce the congestion on the roads, and we’re very grateful to hear that, we still have absolutely no idea as to what the increased level of traffic will be.

“I have been with this project since before 2010 and here we are, this far down the line, and we still don’t know what the biggest impact is going to be on this community.

“I'm looking for some positive feedback from you guys to say ‘this is what we are going to have. You’re going to have delays and it is going to last this long and this is what we are going to do to mitigate it’.

“All we want is some facts, so we can accept it, because this is different to most other developments. In most other road or rail developments, you get a benefit from it. This community is getting absolutely no benefit from it.

“We’re not getting the benefit, we’re going to get the pain. How bad is it going to be?”

Cllr Nick Rose, who was chairing the meeting, added: “There are scores of people who need to travel from one side of the valley to the other and they are worried sick that HS2 will cause them endless delay and aggravation.”

David McCann, engineering manager for Chiltern, insisted the information on traffic and congestion would be made available to residents as soon as they knew.

He said: “It is unfortunate that it’s something we can’t give you now but we need a certain amount of time to develop the numbers – it takes a lot of work.

“Stage one  of the project will be complete at the end of November and at that point we will be informed about what the impact will be and as that information is revealed, we will give it to you, but I can’t jump the gun and give you the information. I give you a commitment that we will share the information when we can.”

David Eve, from Align, a consortium of contractors working on the project, added: “It isn’t in our interest to clog up the road because it means our vehicles are clogged up as well. We are well into the planning process, we will have some numbers but we’re not there yet.”