Mystery markers on the minimap

[ttakalo]

The minimap at the corner of the main game screen has been showing some odd markers around a specific location. That being the highway intersection near the center of the Central area. The markers are grey, which suggests uncollected collectables, but they do not correspond to anything else the map shows. Furthermore, they only show up in the minimap, but not in the full map screen. I cannot actually find anything unusual in the marked locations. Any idea what is going on here?

I have a screen capture of the minimap here: http://i191.photobucket.com/albums/z285/Crowley9/SDminimap_zps8bxnbtfs.png

[newman]

I believe those are jumps you can drive through in cars. They only show up after you've done them once.

[Samson Miodek]

Shortcuts useful when you want to shake off your tail.