The vindictive side of me wants you to put spikes in the yard and pop some tires. :P

If you wanted something to match the look of your house, I would buy bricks the same color and line them up at an angle ///// along the edge, then plant some hardy dark green foliage behind. I don't know if liriope grows up there. Or maybe some dwarf hollies if you wanted something taller.

Any barrier you choose will deter normal people from using your lawn as a parking lot. However, it will not cure drunken maniacs like that last straw guy you just described. (But the spikes can't hurt)

I'm gonna say a row of boulders. Big boulders, like placed by a loader, not just little rocks. If you can lift or even roll it, it's too small. You want something that won't be damaged when people run into it; instead, the damage will be to them.

Boulders are fabulous landscape design elements and you can have lots of fun planting around them, since mowing up to them is a pain. I would make sure they are well lit, so clowns can't claim they didn't seem them when they run into them, which they likely will. So put plants on the outside that can be run over, like hostas and other perennials, while your more costly shrubs or dwarf conifers can be on the inside.

Do place them with some sympathy for the turning motorist. Who knows why they choose your place - but maybe they've just taken a wrong turn and it only becomes clear right about when they reach you. Your best defense might actually be to make sure that there IS a way to turn around easily, but for the clowns, well, for them you have the boulders.

You don't need a solid row of them, unless you get some that just lend themselves to that. They can be spaced, but not like sentries... think groupings, with varying sizes.

KarinL

How about a row of large ornamental grasses such as Miscanthus 'Yaku Jima" (fine texture, get to be 8'across and 6' high) or a little smaller like Miscanthus "Morning Light (about 5' diameter, and 5' high, fine texture, variegated, looks very nice). This makes for large object that deter parking, but won't kill anyone who makes an error and will recover nicely when damaged. You could even space them several feet apart as long as they are close enough to deter parking. ... this is also not an expensive solution.

May I second Laag's excellent recommendation!

I looked at photo #2 and thought "boulders", but I see karinl has already made the suggestion. I would put a few at the places the cars have driven on your property before, the likely but unwelcome entry points. A light-colored stone will be visible in headlights. Then use laag's grasses for the rest, but maybe include some that are not so tall? So you don't cut off your view?

Two years ago my brother watched a guy who was a passenger in a car die on my brother's front lawn after a car with a drunk going 80 mph in a 35 zone hit a telephone pole. I'm very sure I don't want something like that to happen from hitting a rock that I placed near the edge of the road. It may never happen, but boy it would be a burden that would eat at you for a long time. I recommend a soft solution.

Laag, I did think of this. The flip side is that I have read more than one article about cars going into houses, and sometimes that doesn't go so well for the people in the houses OR the people in the cars.

The OP does want low, so would perhaps interpret the "boulder" idea as being just large rocks, maybe up to 18 inches diameter, not three-footers. So hopefully would not be fatal in the event of an accident. But also, this being a straight stretch of road, the problem seems to be turnarounds, thus slow traffic, not people losing it on curves.

Drivers need to come to terms with the fact that dangers lurk off the side of the road - cliffs, ditches, natural rock walls - as well as vulnerabilities - kids in yards, etc. It's a solemn responsibility, driving.

I do like your idea of substantial grasses, if it works - it's certainly cheaper and faster so may as well start with that. They have to grow in though. If rocks are used, either few or many, I totally agree with the rocks being light in colour or otherwise equipped with lights or reflective material. Hmm, I think I may finally have figured out why some people paint rocks white!!

KarinL

I've put boulders in front of people's houses in the past. I am much more inclined to do anything I can to have a softer alternative these days.
If anyone does do this, make sure that you know exactly where the road layout property line is and keep the rocks on your side of it. Not only will you have to live with a death or injury should something happen, but very likely a law suit as well.
Many people assume that the edge of pavement is the property line or that the pavement is exactly in the middle of the road layout. I just did a plan for someone where there was twenty feet between the pavement and their property line. They have a second driveway that is entirely outside of their property. I have 9' between my property line and the pavement at my house.

You might want to contact your state or county (whoever's responsible for the road) to find out what their guidelines are for trees, fences, etc.

I live on a state road in a semi-rural area (45 mph, but also speeders and tractors). Unfortunately, there's no shoulder. The state dictates what can be planted near the road, and mandates drainage ditches on the uphill side of the road (my across-the-street neighbors have the uphill side, and their ditches vary markedly in depth). Interestingly, on the downhill side I have a larger area that can't have trees ... though some of the neighbors do have large shrubs close to the road. Periodically, the state comes through with huge saws-on-wheels to eliminate any offending plantings. (I have daylilies planted 3-4' from the edge of the road, and the state crews don't object to them.)

I found all the details online once, but didn't keep a link and now can't find it. 8-( Supposedly I'm prohibited from planting a tree within 15 or 20' of the road ... yet some of the other "lower" properties have them closer....

The previous owners' survey indicates the state has authority over the first 15' of "my" front yard.

There is something to be said for the term 'genus loci' or 'a sense of place'.
Your rural setting , the style of your home and the surrounding landscape would lend itself well to a well built split rail fence. Classic and enduring in design for your site. Simplicity in its character, empathetic to your site challenges.

If you feel like jazzing it up a little you can weave in a planting of perennials and ornamentals grasses for color and texture and visual pleasure.

Your property looks well-loved and cared-for, as well as peaceful, except for your uninvited "guests". I'm in NJ, too - southern Monmouth County.

I'm glad to see some of these recent posts, though. The dangers of the boulders (and lawsuits) are very real, and it is important to identify any easements the municipality, or any other entity, may have. Our property line is 10 feet from the paved road (no curbs or sidewalks). And with that straightaway, you probably get some pretty fast-moving cars at times, too.

A sense of place is also an important point. Annie, from the photos, I'm thinking maybe you're in southern NJ? While some parts of our state are very rocky, a lot of others are flat and sandy and boulders just look contrived and out of place, IMHO, no matter how carefully one chooses and sets them.

I tend to agree with deviant-deziner on the split rail fence. Once they age to a silver gray they blend very nicely with their surroundings, and you can soften the look with a mixed border of shrubs, small trees, perennials and bulbs if you like. Choose the right plantings and it will be fairly low-maintenance, provide year 'round interest, and habitat for wildlife (I'm thinking birds and beneficial insects ... do you have deer? Looks like prime real estate for them. If so, you'd need to choose plants they won't munch on.)

Ah, the summer sport of mailbox batting. I'd never heard of that until we moved to the shore area and I thought it was a shore thing mostly perpetrated by ... um ... non-residents. Folks here have come up with a variety of bat-proof solutions: mailboxes enclosed in brick or stone columns, attached to I-beams, wrapped in heavy rope (the nautical theme can work here). You can get pretty creative.