One light year is approximately 10 trillion km (actually 9.46 trillion km) (or 6 trillion miles (actually 5.88 trillion miles)
Total vehicle travel in the US is approximately or 3 trillion miles (2.968 trillion miles in 2012) . So in the US, vehicles travel 1/2 of a light year each year.
The nearest star (which is not the Sun) is Proxima Centauri, which is 4.2421 light years away. If instead of driving around hither and thither, mostly in circles, we established a giant relay, we could cover that distance in 8.4 years of American driving .
Now of course, it takes a year for light to travel a light year, and cars don’t yet travel at or near (much less faster than) the speed of light. So at an average speed of 100 km an hour, it would take much longer (about 11.4 billion years) for one car to actually drive from here to Proxima Centauri.
This example would require somehow prepositioning all the US cars along the way (say at 100000 km intervals), and the letting them do their annual driving for 8 years (i.e. each would drive 100000 km). This then requires us to construct a space highway, say the Hoober-Bloob Highway, or perhaps a very short section of the Vogon Intergalactic Highway.
At any rate, this gives you a sense of the scale of space .. it is so large, all US traffic only goes 1/8 of the way to Proxima Centauri; or it is so small, it only takes US traffic 8 years to go to Proxima Centauri.