"I saw a lot... about 40 of them... and I thought, 'oh no, I'm in trouble'."
With cars behind her and unable to turn around, Riva said her only option was to put her foot on the gas and drive as fast as she could. She sounded her horn in a desperate attempt to alert other drivers to the ambush - and then was herself subjected to "the most terrifying experience I have ever been through."
"I just took my hand and covered my head and just rode, ducking, with my hand on my head.
"The sensation was like... it was literally like a rain of rocks. Pieces of construction material - big rocks, even bricks," she recalled.
"There must have been 20 rocks bouncing off my car. I have never experienced such a terrifying moment like that... I was fortunate that they didn't block the road as well or God knows I wouldn't be talking to you now."
Her car suffered severe damage but - though shaken - Riva's quick thinking helped her avoid any physical injury.
But it could have been much worse. Rocks had shattered through her back windows - some with such force that they damaged the windows on the other side of the car - precisely where her elderly parents-in-law were meant to have been sitting at the time, but were not due to a last-minute change of plan.
"They would have been killed, no question," she says.
"I've had a firebomb thrown at my car - which fortunately missed me - I've had rocks thrown at my car, I've even once had a machine-gun fired at my car..."
"I've been through it so many times... after a while you get 'good at it', which is extremely sad.
"The worst part of it was... I was trying to take my phone out while I was driving, and trying to see if I'm safe yet to call the police because of the people behind me, who would be walking into an ambush.
"I know there were plenty of cars behind me, so others were also attacked for sure."This hits really close to home. We drive to Beitar - and to Beit Shemesh by way of Beitar - way too often
After driving a while longer she finally reached Betar, where she immediately alerted security guards, who called the military.
In the meantime, the government, in its infinite wisdom, decided today to impose a 20-year prison term on people who throw stones at cars. That's not an effective deterrent, because (a) everyone knows that the stone throwers will be released in exchange for some kidnapped Jew anyway, (b) they aren't likely to take 10 and 12-year olds (yes, some of the stone throwers are that young and younger) and put them in jail for 20 years, and (c) the law only applies in Jerusalem.