I-10 in Phoenix near Sky Harbor - perfect shot with the aircraft about to land:

I just wish the polarizer didn't cause so much vignetting in one corner...
Usually the vignetting happens when the darker shades of blue are present depending on which way you turned the polarizer filter. If you turn it one way, it would deepen the greens and blues and tack off some of the annoying glare, which works well on reflective surfaces, so, the vignetting is essentially noticeable because of the angle of your polarizer and where you were aiming to shoot the picture. In some cases the vignetting looks cool, but, I guess in your case, you weren't expecting the vignetting to occur. You'd just have to turn the filter the other direction to lighten up the corner before you shoot again. In post-photo, I'd look for some filters to brighten up that corner that was caused by the filter being turned. Which, evidently, you deepened the green and the shadows of the light brackets and removed the glare.