Long story on 540. It was built circa 1970 as a 2-Lane bypass of Fayetteville. It was expanded to 4 Lanes in the name of safety after too many accidents. It later got tied into I-540 which had been in the planning stages since the 1960's.
There have been some recent improvements on 540:
The US 62 Interchange is in the final stages of bring rebuilt, Porter Road was recently rebuilt as was Wedington Dr (AR 16) and New Hope Rd/Pinnacle Parkway. Most of this applies to the side roads, though, and not 540 itself.
Part of the problem is the area surrounding 540 is commercially overbuilt . I have seen plans for 6-Laning 540, but it's a matter of $$, which they don't have. IIRC, at least 2 motels could be affected and knowing the owners (and I DO), they will want a lot of money for their land.
John Paul Hammerschmidt delivered the pork that built 540 from Alma to Bentonville, but he's no longer in office. And 540 isn't on John Boozman's radar at all unless he's complaining about government deficits.