As the VW emissions scandal draws a (potentially brief) breath following the resignation of CEO Martin Winterkorn yesterday, there is a sense that the firm's cheating of the system could plunge the entire car industry into crisis.

VW's cheat has put the focus on emissions testing as a whole, and the undeniable truth that laboratory tests do not reflect real-world use in any realistic fashion. We knew that, of course, and our sister brand What Car? created True MPG for that reason, but it seems only now the wider world has woken up to it.

Changes to narrow the gap have been planned for some time, negotiated between regulators and car makers. Now, with governmental focus pushed on the issue by VW's fix, these changes may come sooner and with fewer concessions.

But regulators must resist knee-jerk reactions, not least because it is the regulations - as opposed to the car makers - that have been found wanting. Every major industry is regulated, and from pharmaceuticals to construction to car making the money makers work to the standards they are set.

Measuring emissions is complex, not least because so much depends on the driver. What feels painfully obvious today but perhaps wasn't last week is that the obsessive focus on CO2 in Europe at least has taken the collective eye off the ball on NOX.