Generally, for ergonomics and economics reason 4ft width is about right. So you can easily reach 2ft from each side comfortably. .

Four foot wide is also practical for planting 2 rows of tomato plants, each row located one foot from their respective side. This will leave 2 feet between the rows. IMO that is adequate row spacing. Actually I plant 2 rows in 3 ft wide beds.

Sey

I have one 50' long 18" wide bed on a terrace that gets used every 4th year for some tomato plants and they do ok in it. It isn't optimal IMO so I do increase the plant spacing to 4' center to center when using it vs. my normal 3' sq. spacing in the hopes of allowing greater lateral root growth. End of season when plants are pulled you can't tell where one set ends and another begins.

Dave

You'll be fine as long as you don't plant them too close together.

Narrow beds that prevent you from trying to fit extra rows into the same raised bed may actually be better for plant health. Worry more about having air movement through plant canopy to prevent foliage diseases and much less about root space.