As alluded to earlier the Heathrow Express 332 EMUs were designed without a yellow warning panel to resemble a crash helmet. I believe the units were already built when word came that the rules weren't going to be changed. Warning panels were added but never quite looked like a smooth part of the design. Compare these to the similar 333s where the yellow panels look part of the build. I believe when the 332s were refurbished recently they received revised yellow panels which look a more natural fit. Out of interest, if the 332s worked only on the Heathrow owned spur could they be warning-panel free?
I think the HSTs used the warning panel beautifully with body side extension remaining into the first incarnation of IC executive livery. The early sliding door stock also had yellow wrapped round - the 313s angled, the 455s more stunted. The blue-grey 313s were also slightly odd for having black centre doors to offset the yellow cabs.
Weren't there issues with the 442s too. I think the Stagecoach South West Trains livery originally envisaged more orange and less yellow.
The discussion of Network Rail got me thinking about the old class 97/6 Ruston & Hornby shunters which were painted yellow with was stripes at the front. Looking at photos on Google Images it's hard to tell if it's the same shade of yellow.
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The 332s without yellow front ends. No denying they were stylish and rather futuristic at the time but silly of the designers not to be abreast of the rules.
http://www.railway-technology.com/projects/heathrow-express/heathrow-express6.html
