At the UK Commercial Vehicle Show in Birmingham, six months on from Euro IV emissions legislation coming into force, one thing was clear. Even those truck operators who brought forward their fleet renewal programmes last autumn, in order to avoid the up-front costs of compliance, are now having to review their often long-standing brand loyalties.

Thanks to the 'great deNOx technology divide' between SCR (selective catalytic reduction) and EGR (exhaust gas recirculation), the battle for so-called conquest sales has taken on a keener edge. Manufacturers in the SCR camp, namely DAF, Mercedes-Benz, Volvo, Renault and Iveco, are keen to woo established buyers of MAN and Scania chassis, whose Euro IV models are EGR equipped. The promise of improved fuel economy from the SCR alternative, especially crucial on high-mileage operations, was initially the main inducement.

But a new SCR trump card was starting to be played at the CV Show, that is the system's potential to 'effortlessly' meet Euro V standards. Bringing NOx levels down, from the Euro IV level of 3.5g/kWh to the 2.0g/kWh demanded at Euro V, is much more challenging with EGR technology. Scania however plans to introduce the first of its Euro V compliant EGR engines at the RAI show in Amsterdam next October.

The UK government's reintroduction from October 2007 of its Reduced Pollution Certificate (RPC) scheme - albeit in a revised form - offering VED (vehicle excise duty) reductions for trucks certified to Euro V emission standards ahead of the October 2009 mandatory compliance date, served to bring SCR's attractions into sharper focus at Birmingham.

Among the UK show exhibitors championing EGR, including Hino and, at lower weights, Mitsubishi Fuso and Isuzu, the operational attractions of avoiding the alleged hassle of AdBlue replenishment continued to be trumpeted. Not having to sacrifice the payload or chassis space needed to accommodate SCR system componentry is another key benefit of EGR. In the weeks after the show, those considerations prompted Volvo - otherwise fully committed to SCR - to announce the imminent availability in Europe of an EGR version (engineered primarily for the North American market) of its mainstream 12.8 litre heavy-duty engine.