What will be the most suited remote sensing data to use for mapping highways in North America?
I assume you are going to apply an automated classification algorithm to detect roads in the imagery. I would recommend two products: 4-band NAIP imagery at 1m spatial resolution and Landsat 8 (15m (panchromatic)- 100m (SWIR))--both of which are free and available from Earth Explorer and from a variety of state web sources. The 30m Landsat data would be particularly useful for mapping large highway systems across the entire USA. The SWIR band may prove useful in your classification algorithm due to its ability to represent emissivity off hot (paved) surfaces. On the other hand, NAIP imagery has much higher spatial resolution (1m) and is suitable for hand digitizing features and classifying roads in localized areas. As a point of reference, 4-band NAIP imagery for the state of Wyoming is about 1.2 TB in size.