Three Hitchin junctions would see major investment if Luton Airport's expansion gets the go-ahead, according to plans.

Facing questions from planning inspectors, Luton Rising – the airport's parent company – said its plans for Hitchin will "improve traffic flow" in the town.

But the panel of inspectors, known as the Examining Authority (ExA), warned it may not have enough information to form a view about an expanded airport's impact on Hitchin.

Jagjit Riat, a transport planner on behalf of Luton Rising, told the ExA there are three main junctions which would need work to support more passengers.

"They are existing roundabouts which are relatively constrained in terms of what we can do with them," Mr Riat said at the hearing on Thursday, September 28. We believe the highway works we are proposing enable better traffic flow through the network."

Hitchin lies between the A1(M) motorway and London Luton Airport. Transport planners simulated how traffic would behave in the region – as far away as Letchworth, Sandy, Aylesbury and South Mimms services..

In Hitchin, the junctions "requiring mitigation" include the A602 Three Moorhens pub roundabout, where the A-road and Hitchin Hill could be widened to two lanes on the roundabout approaches. The two-lane approaches to the A602 Park Way and A505 Upper Tilehouse Street roundabout could be lengthened.

The Upper Tilehouse Street mini-roundabout with Pirton Road would also see changes – with a two-lane approach to the junction for A505 Luton-bound traffic.

Elsewhere in Hertfordshire, Luton Rising's team indicated it could support "traffic calming" in Whitwell, Great Offley, Breachwood Green and Tea Green.

ExA: 'Will these works solve Hitchin's traffic woes?'

A 54-page traffic modelling document forecasts what could happen on local roads in two scenarios. The first scenario looks at what could happen if Luton Airport remains a similar size, and very few highways works take place. In this case, planners expect drivers will make 20,257 journeys on the A505 Upper Tilehouse Street in Hitchin by 2039.

The second scenario looks at what could happen if Luton Airport does expand to accommodate 32 million passengers per annum (mppa) – up from today's 18mppa – and completes the highways works. The model shows the number of average daily journeys on the same stretch of road would rise to 22,083 by 2039 – a nine per cent increase.

But there is no study of what could happen if Luton Airport expands and highways works do not take place. Without this information, there are questions over whether highways "improvements" will be effective, the ExA suggested. The panel asked: "How do we know whether what you are proposing is going to solve problems?"

The ExA tasked Luton Rising with coming up with an answer during the course of the planning process. Mr Riat said there are "different iterations of design" which the team can go through to come up with more detailed answers.