I learned how to do the starting on a steep incline ..using hand (emergency) brake, clutch and gas...out of a need to avoid crashing into the vehicle behind me...on a slope.
My first car, a '61 VW Beetle was my vehicle at the time.
Studebaker actually had a device called a 'hill holder' that accomplished this process.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact...iYQgzQwd8WioUf
Way back around 1971, I was a university student who also drove a variety of commercial trucks for a company I worked for. The company was very generous and allowed me to take different trucks home for the night and I would drive them to U., than work, immediately after classes.
One early morning, my mother and a neighbour lady were waiting at a bus stop, late to work as there had been a snow storm that previous night and traffic was badly delayed in the city. I asked them to hop inside the truck and I would get them to work. Unfortuanelty the truck I was driving at the time, was a large commercial van...it had just the driver's seat and no where to sit, except for a couple of upended wooden boxes...and two inner wheel wells over the rear axle's wheels/tires.
The ride was uneventful, until I was stuck on an underpass incline..on an icy, snow covered road. The truck had a manual transmission and an on/off lever actuated emergency brake...the brake lever was on the left side of the cab.
Traffic started to move and I let out the clutch..the truck couldn't get traction and started to slowly slide backwards...I could see a late '60's Rambler in my side mirror...panicking with his front wheels crossed...wondering if my heavier truck was going to slide slowly into him. He was at the bottom of the hill about 15 feet behind the rear of the truck.
I hit the brakes to hold the truck..directed my mom and her friend to choose one wheel well each and sit on it...'for traction'... I yelled. They started laughing
at the thought of them being regarded as mobile traction and promptly sat on top of the inner wheel well of their 'choice'.
I put the truck in 2nd gear...slipped the clutch a bit...slammed the emergency brake on and off...and the truck started to get traction...think the effect was to give the truck...sort of a locking axle...using the emergency brake and slipping the clutch. Whatever it did..it worked..yeah the axle hopped a bit, but the truck got traction and mom and her buddy got to work...no worse for wear.