Responding to this week's announcement by transport secretary Ruth Kelly of a feasibility study into opening up 800km of motorway hard shoulders to traffic, NCE was told that such a project must not be "value engineered".
The warning comes following an announcement by Kelly of a new study that would focus on "large sections of the M1, M6 and M62" as well as the M27 near Southampton, the M4/M5 near Bristol and sections of the M23, M20 and M3.
A Department for Transport (DfT) workshop on hard shoulder running on the day of the announcement, which involved engineers from the Highways Agency and motoring groups, heard that any new schemes following on from the successful £150M pilot project around the M42 in Birmingham could be "value engineered".
This could involve less overhead gantries warning drivers that the hard shoulder was opening up and displaying variable message screens
and less refuge areas for broken down vehicles.
"If we roll out active traffic management we have to do it properly," a source told NCE.
"The Highways Agency already seems to be suggesting that it overengineered the M42 active traffic management scheme and we fear there is a wish to reduce the engineering on it as it rolls it out to spread the money more thinly over a wider area."
Gordon Clark, chairman of consultant Gifford, which designed the gantries for the M42 trial around Birmingham, said changes and economies of scale could enable hard shoulder running at a cheaper construction elsewhere in the country.
"It may be possible to cut the number of gantries by slowing speeds down on the approach [to hard shoulder running sections of the motorway]," said Clark.
"But with such repetition over such a wide area we could achieve value for money because of the economies of scale."
A DfT spokesman said: "We will make sure these schemes are effective and safe. Whether they are exactly the same specification as the M42 we can't say at the moment."
Kelly also announced that the Transport Innovation Fund for local authorities interested in setting up demand management measures such as congestion charging would be extended for another four years until 2018/2019.
This, in effect, rules out a national road pricing scheme before 2020 as the government has previously said it would assess the success of local schemes before pursuing a national scheme.
However, only Manchester and Cambridge have so far come forward with definite TIF proposals for congestion charging. "It is sensible to recognise the time it takes to develop and deliver these schemes," said Devon County director of environment Edward Chorlton.