When assessing an area for safety what are the MAIN four hazards that you need to avoid?

I would just like to know 4 main hazards - the most important ones - please:)
Thanks.

one Helmets are good, though I can't wear them.
two - Stirrups are very dangerous, if you can't keep them toes up, heels down. Buy break away, escape stirrups for your Horse, more riders are killed every year because of this!
Three - Desensitize your horse for traffic, people, and Bikes, and most of all those big trucks. If I feel as if my horse is going to spook from traffic as trucks and tractors go by us, I will get off. Reward your horse after she/he gets your trust.
four-Watch out for kicking, as when you are cleaning out your horses hoofs, work with your horse day-lie when cleaning hoofs out, remember the farrier is not your trainer You are!
Most of all, all of this can be avoided, after you win your Horses trust, as I am riding down in heavy traffic, and there may be a big truck coming, I just sit deep in the saddle, and then she can feel my relaxation, in the seat , which will help her relax also, if she starts to spook, I just let her know, It's going to be okay, soothing her neck. pets question and answers,www.5d2d.com
Most important, let your Horse know, his space. I have been trampled twice from yearlings, when something comes up from behind them, let it be just a peace of paper blowing in the wind, or another person, and the horse wants to jump into your pocket for protection, so let people know, that they should talk softly, when coming up behind you and your horse.
I know I gave more than four, but the list even goes farther.
Just get a good bomb trained horse that has never been beaten or abused and you should be just fine .
I hope I had helped some.

Trainer 50 years

Hazards to avoid in any given area you would possibly be riding in:
1) Sharp objects: improperly stacked jumps, farm equipment, or broken fencing.
2) Loud, aggressive, or inexperienced people, drivers, and dogs. (feral animals are not really dangerous unless rabid, or of the predator type like cougar or bear)
3) Bad footing: nails, glass, holes, other dangers to the equine hoof and legs on the ground.

pets question and answers,www.5d2d.com

4) Weather considerations: Lightening, extreme heat (stay out of the sun and dont 'work too hard, keep water available), Gusty wind (falling or loose objects then become dangerous), and ice or other slick surfaces causing horse to slip or lose footing.

I'll assume you want to assess an area for riding in:
Enclosed area: If you fall off you don't want your horse to run off and get lost etc.
Even surface : You get the best work out of your horse on a nice flat and even surface and any potholes or anything of the sort may cause the horse to trip and possibly fall.
Spooking opportunities: Make sure there is very little/nothing for your horse to jump at, that way you'll be safer in the saddle and you can get your horses undivided attention for work.
No sharp edges/objects: Unlikely but if your horse brushed against one or possibly chucked you off into one it'd hurt! also clear the ground you're working on so there's no big stones or nails etc.
ALWAYS make sure you have a kite marked hat, body armour if appropriate, tack is fitted correctly and boots if appropriate (though I'm sure you already know this!) xx

I'd say:
1) Safe footing-Gives horse enough traction, no holes, glass, bits of metal, large rocks, etc.
2) Environment-not right next to a busy road, no dogs/small children, etc going to run into your path, crazy people firing rifles, etc.
3) If in an arena , the fencing or containment. No nails sticking out, broken fence boards, arena walls are an appropriate height so horses won't jump out, appropriate size riding area, etc.
4) Weather-no storms or dangerous weather in your area.

well, you didn't say what type of area, so I'll just take a guess:)

IN AN ARENA: You need to make sure the fences are solid, incase the fence falls and the horse spooks.
Make sure there are no sharps or foreign objects hanging off the fence or laying on the ground s the horse may spook or hurt itself.
Make sure there are no holes in the ground of the arena, so that the horse doesn't trip and hurt his leg.
Make sure the grounding is soft enough to ride on, and there are no roots in the ground. pets question and answers,www.5d2d.com

OUT ON TRAILS/PADDOCKS
Make sure there are no sharp obstacles in your path
Make sure there are no feral animals around
There are no 'scary' objects
Always make sure your horse is wearing boots

I hope this helps

1 - Let someone know your ride plan, location, approx. return time.
2 - Carry your cell phone on your body, not the saddle bag. If you fall & your horse flees, so does your phone!
3 - Be in tune with your horse, ears, eyes, body language will give a rider a heads up on approaching trouble.