It is fairly common practice to drive to a trailhead, park your vehicle and then go backpacking for a while. It would be a real bummer to come back from a trip and find that your vehicle has been broken into.
Are there any tips to reduce the likelihood of this happening?
One of the deciding factors for thieves with cars is whether they can see something they consider of value. If they have it fixed in their minds to breaking into your vehicle, they will do it.
Here is a few things I do to avoid such misfortunes:
It sounds counter intuitive but leave everything inside the car open, i.e. the boot cover glove box, etc. Make it obvious that there is nothing worth stealing inside (and obviously don't leave anything worth stealing).
Don't worry about them stealing your car, this is practically impossible with modern security devices (the only way to steal a car these days is by stealing the key due to immobilisers, etc).
Still doesn't protect you from random acts of senseless vandalism but, well nothing can do this really.
The existing answers by Ken and Liam offer good advice. But unfortunately there is nothing you can do to prevent break ins. Thieves can be surprisingly stupid.
True story...
A friend of mine drove her jeep wrangler with a soft top to the trail head and parked it before going on a hike. The roof is canvas and the back side window unzips FROM THE OUTSIDE. She left the doors unlocked, so if someone felt a strong urge to rifle through her jeep they would not be inconvenienced and feel the need to damage the canvas top.
The thief did not even try the door, nor did they unzip the side window. They used a knife to slice through the back side window (plastic). Opened the (already unlocked) door from inside and rifled through the jeep finding nothing worthy of stealing.
No there is nothing you can do, to prevent breakins, even leaving the doors unlocked will not prevent a break in.
Image link of similar vehicle: Jeep Wrangler.
Basically, the same rules as elsewhere apply. I’d stick with those:
Still, as everywhere, there is no 100% security. At the best, these things reduce the likelihood of something happening.
One thing that has not been mentioned is to consider which trail head you park at. Some trails/areas have multiple trail heads. If you have a choice in trail head, it is worth talking to locals to determine if any are particularly problematic.
In my experience the most problematic trail heads are those with easy access. What this means is that often if the only available trail heads are problematic, that there are alternatives to parking directly at the trail head. Sometimes you can park in town (e.g., Walmart in the US or an outfitters) and catch a shuttle, hitch, carpool, or even bicycle to the trail head.
If you can't leave the car empty-looking, at least don't load the storage up at the trailhead. There was a spate of thefts a few years ago on Dartmoor where car parks were watched for signs of valuables being tucked away, then a window was smashed and the items stolen. This was the sort of place where cars are parked for hours rather than days. In our case they knew which side to smash to be able to reach a handbag. This was an estate car with a soft luggage cover; that seemed to be a bit of a theme when I looked into it after the event.
So instead, get your bags ready before the drive, and pick them up off the back seat when you leave the car. Any valuables you want on the drive should go with you. Then leave nothing on show that could look like it might hold valuables.
There ain't no way man...As Mr. Miyagi would say, "the best defense against a would be car vandal is no be there."
I propose a different solution than others would:
I never have that problem because I do not park at trailheads. We have been known to pull our 1999 Toyota Corolla off the dirt road we were on ( another tip: find those dirt roads! ) and cover it up, even if it meant building a small lean to over it. Since we were already driving in a very deserted area not turning off a major highway and into a crowded trailhead we would just camp close to the car and we have never had a problem.
Sometimes, I bike to the trailhead after parking in Walmart's heavily watched parking lot a mile or so away. Or, I sometimes leave the car at home and bike all the way. Yea, down the trail and off of it too a good mountain bike will go.
If your vehicle has a trunk that can't be reached from the cabin, then physically disable the trunk release lever by detaching the cable. Objects in your trunk will only be accessible with a key, or by a very determined thief with a crowbar.
The biggest thing is to plan ahead. Whether you are going to a trail head or to a show in the city... Don't think that a towel for a cover or sliding it under a seat will work. Stow stuff in your trunk before arriving. And hopefully you have a lock on your trunk button.
Great suggestions here; I would add I concur with the leaving car empty of all valuables, glovebox open. Additionally, you could buy a car camera with live feed and GPS capabilities. They are available and not too expensive. A "warning sticker" or two, placed prominently, might do the trick just as well. Akin to putting a security sign on your lawn and decals in the windows of your home. It has deterrent value and potential thieves may well go for a less intimidating vehicle.
Although it may seem extreme, I often disconnect my battery before embarking on a hike. Especially if I am in a remote location. This is a nice way to ensure there is no slow electrical drain that may discharge the battery. Additionally, it would hamper a would-be thief’s efforts at stealing the car. If I must leave something of value in the car, I try to hide it either under a seat or in the spare tire compartment, hoping that the thief is too lazy to search thoroughly. I have also used personal alarms such as these:
Street Wise 72-SWPPA SWSB22 Streetwise Personal Protection Alarm
They are easy to attach to a backpack or bag left in the car, and if the thief removes the bag, the alarm goes off. Might be enough to cause him to run off.
There are already loads of good tips here as I add this, but I'm missing one in particular: if you have to leave electronics behind (for some reason you can't leave them at home, like maybe you're doing the hike on your way somewhere), in particular larger items like a laptop, shut the device down (or hibernate, not sleep) and take the battery out of the device just to be sure. Theoretically thieves can detect a device in several ways, including finding the electrical charge itself (against which the removed battery would help), but the easiest thing to track inside a metal car in practice is the wifi signal. This can at least on some models even be detected in sleep mode. Make these preparations before you're at your parking spot because as others noted thieves can be watching. And there are way more thieves with eyes than with wifi detectors.
While I'm writing anyway, avoid leaving expensive sports equipment in sports related locales. Thieves go to these trail heads because they're trail heads. It's mostly not an issue with walking, but a thief visiting say a cross country skiing trail start might know a thing or two about which skis are resellable. Similarly kayak exit points and campings are visited by thieves who know their boats. If you have to leave stuff, lock it up someway, make them work for their loot.
1,5 year old question, but I do not see this trick which I (also) use:
Make the car and its content look shabby and uninteresting (that is more 'extreme' than the earlier suggestion avoid leaving hints of something valuable being in the car): dirt and a few old rags or newspapers make you car shout out this person has no valuables.
