The source is wrong.
NO/NOx is a problem in general, I don't really see why cars are being labelled a major factor, to fix a problem you need to find the source and cars are far from the source.
From the look of these 'tests' (there are videos online), shoving a bee into an exhaust will impair the best of senses, lets face it, if you fill a car with exhaust fumes and sit in it, you die.
NOx is smelly, it's not a food and the bee won't react to it... and slapping a single bee on the head provoking a signal for incoming food after they trained it that way - or did the scientists seemingly fail think of this? Somewhere an education system has failed again.
I half heartedly believe that NOx has a major impact on their ability to detect flowers, especially since the majority of flowers preceding in my garden produce little/no scent, but are extremely vibrant and well pollenated by bees... as are most bees are accustomed to in high NOx areas.
Diesel does produce NO/NOx, but so does petrol (albeit lower), so changing the fuel won't resolve the issue, it will delay the inevitable, especially since this year has hit a 5 year high of new vehicle registrations.
Fracking can cause large amounts of NO and NOx in the atmosphere, equal to that of coal burning and turning all cars to electric ones won't fix the issue, far from it.
Fun Fact: Coal in itself causes more pollution in the air than it's own weight - the very same coal that attributes to the power coming out of your wall socket at home. Electric cars are funny, this will just push the pollution up more.
Whilst technology is reducing the amount produced per X amount of coal, the demand for power is outstripping the benefits as our population is constantly and rapidly expanding, with that there will be more vehicles, more homes to power, which means more emissions.
Alternatively, finding ways to break down NO/NOx would be ideal, back in 2012 "photo-catalytically active" paint was created, this breaks down NO/NOx into nitrates (with the bonus of self-cleaning itself) and extremely small amounts of CO2. I believe you can buy it online, its called "KNOxOUT" produced by Boysen. I have absolutely nothing to do with the company selling this product by the way - but it is a 'light' at the end of the tunnel and something that's worth looking into.
Additionally and always, cycle to work if you can, turn off that electrical appliance if you aren't using it and invest in some solar panel battery chargers, they really work (saving a ton in energy bills) and with technology nowadays are getting better/cheaper, there's really no excuse!