Since I've never learned to slide (whereby you can control yr. speed), I need to get off the board before getting to the speed where I can't get off and remain vertical.
For now I'm just skating gentle slopes and carving. No (well not much) bombing. I wear Loaded gloves with hockey pucks velcroed to the palms. Cliff Coleman, downhill speed legend, told me that when you fall, remember 4 words: Get On Your Hands. Meaning get those hockey pucks sliding on the pavement so you're not sanding off skin.
The other part of the equation is to also slide on your knees, i.e knee pads with hard surfaces, so you're on all fours, sliding on knee pads and hockey pucks.
The one time I had the presence of mind to do this was in San Francisco late at night when my board hit an unsurmountable crack in the pavement, and I skidded along on 4 noncorporeal surfaces.
Boards shown from my, ahem, sponsors: at right my smooth turning, stylish carving bamboo Bhangra from Loaded Boards; at left my carvy cruzer with drop-down deck from Santa Cruz Skateboards----for bombing and sharper turns,
On the road again...
Posted from 30,000 feet, pretty good United Airlines wi-fi hookup, 1/3 of the way to JFK. Stylin' it in business class, free ticket from frequent flyer program.