I'm curious about what is the maximum distance you can live from work so that it's a reasonable biking distance.
I am interested in biking about 30 minutes to work. It would be about 5 miles away. I have a heavy cruiser bicycle (Schwinn). It would be a leisurely ride.
A good safe biking distance is the distance that one can enjoy the bike ride to work, get there a few minutes early to clean up or shower and after work enjoy another bike ride home and still spare some time to spend with family/ loved ones/have a life besides work and the commute.
I limit my bike commute to about an hour each way.
It would depend on a lot of things, such as terrain, weather, traffic etc. If you are not sure, simply ride a few kilometers and you would be in a position to guess. Safety hazards increase as you get tired, it will affect your judgment and reaction speed. You can get a guess on that by doing some trial riding.
One thing that is for sure is that the more you ride, the safer you will feel. Your body will adapt to cycling and you will feel less tired day-by-day, and be more confident about yourself on the streets.
Other answers have touched on this but not explicitly. The main safety point I would say is how you ride when you're tired. If you're exhausted and can't keep a straight line up a busy hill, don't think to look over your shoulder in time etc., that's bad and getting dangerous. tiredness can really hit your judgement and reaction times.
Otherwise it depends on your starting level of fitness and facilities in work more than safety. I started from an occasional leisure ride by riding the 9-10 mile each way commute once a week for a couple of weeks, then twice, but not consecutive days. Now I'll happily do 4 days in a week if it fits in, and would try every day but haven't had the chance.
I would say that the bike doesn't make that much difference at the scale of your ride or mine - with the obvious caveat that it fits reasonably well and isn't in a terrible condition or something weird. If it's OK on a cruiser it will be better on a road bike or hybrid (my choice for urban riding given the state of the roads/hills and the need to see over cars), but if you find it horrible on a cruiser, you wouldn't find it a pleasure on an unfamiliar road bike.
Of course, if you're at risk of heart attacks, recovering from an injury or whatever it's a different matter.
Traffic, weather, and geography would make a world of difference. On a dry day at 68°F, 10 miles would be great. If you have to take several pedestrian bridges to cross major arteries in hot, humid weather, even 1 mile could wear on you. I do 1.55 miles with pretty-much no traffic (crossing one semi-major road to get to work), but this Florida weather does makes it easier for me to make excuses during the summer.
Until recently, I was commuting by car about 53 miles to work one-way. I once considered doing the commute by bicycle on a Friday, getting up extremely early in the morning and coming home just-about dead. (We have a shower at work.) If you already have this job, maybe a one-day tryout would be the way to go, or you could try simulating your commute on a weekend.
Not knowing your other factors, I would guess 5 miles would be no problem.
This is not really a safety issue, but one of practicality and convenience. I commute a total of 6 miles each way, every day, rain-or-shine in a humid climate.
The most important thing to consider is not the bike, but your clothing and amenities at your destination. I use a backpack and carry a change of clothes and my laptop (using plastic bags for protection from rain). There is a shower at my work, but I don't use it unless I am truly soaked with sweat (only needed if I take a long "detour").
Even heavy rain is not a problem if you have a change of clothing.
The distance is really up to the individual. If this is to be a daily commute, then you'll need to consider the weather at times. Five miles should be easy to cover with a cruiser type bicycle. It's just that at times when it's raining or the wind is blowing at 25mph, that five miles will seem like ten miles. The safety part will be determined by the condition of the roads traveled, the amount of traffic, and how you must dress for your commute. If the commute will be made only when conditions are acceptable as being "comfortable", then you should have no problem with using the Schwinn cruiser for the ride.
One thing also to consider is a minimum distance. If you are a sweater (i.e. one who sweats) a shower is a necessary part of bike commuting. If you are going to take the time to get all your gear together, pack a change of clothes, and ride your bike, 5 miles is too short. I sweat in 5 miles. My minimum distance is 10 miles, and max is 15. Anything more than that I can't sustain on a daily basis.
I am interested in biking about 30 minutes to work. It would be about 5 miles away. I have a heavy cruiser bicycle (Schwinn). It would be a leisurely ride.
I had a 5-year break from cycling. Before accumulating 100km after the break, I made several >20km rides. The largest of these rides was 28km. Less than 2 hours.
Before the 5-year break, I regularly did 50km rides. Such a ride is 3 hours. However, I wouldn't advise doing 50km rides to work, as I only did one such ride per day. A 50 km one-way distance is 100km per day.
The reason why I enjoyed such long rides and could do a 28km ride after 5-hour break? It's three-fold:
Throw away your current bike if the distance grows to over 5 miles. I'm sure you're limited to 5 miles with a heavy cruiser bicycle. There are bicycles better than heavy cruiser bicycles, and with those better bicycles, a distance of 20 miles may be feasible.
