Thames Valley Police caught 12 drivers on the A34 and M40 in Oxfordshire using phones on a single day during the operation.
It comes after a lorry driver was sentenced to four years for killing a family-of-four by getting distracted when using his phone on the A34.
Police said that one driver was filmed for 30 seconds driving with no hands on the steering wheel.
Chief inspector Henry Parsons said: "Sometimes HGV drivers think as they are high up we cannot see them using a device, but with this tactic we definitely can."
On 31 October Tomasz Kroker was sentenced to four years after he pleaded guilty to using his phone while in charge of a lorry.
After getting distracted he ploughed into a number of cars killing Tracey Houghton, her two sons and her stepdaughter.

Defeats by Munster, Edinburgh and Ulster were followed by a run of nine wins in 11 Pro12 and European games, including a win against Toulon.
Ospreys beat Scarlets 19-9 on Tuesday.
"Hopefully it's just a glitch. We'll see next week if it's a huge step back," Owens told BBC Radio Wales.
"We've bounced back well, we didn't have a great start [losing first three games] but we've built momentum.
"We've got some great performances in during the international period and over the last couple of weeks."
Scarlets are fifth in the Pro12 following the Ospreys defeat but Owens is optimistic about their progress this season after a poor start to their league campaign.
"You can't win every game in the season and, as long as we turn up with a huge win against the Blues, then we'll be back in that winning groove again," Owens continued.
"You can't go all season winning every game, it's not going to happen, so we will put ourselves in a position now from the start we had."
Scott Williams says Ospreys' kicking game proved vital in the defeat and says they need to look at themselves closely before facing Cardiff Blues on New Year's Day.
"We knew it was going to be close but there were too many mistakes and too many penalties," Williams said.
"Our defence has been pretty good the last couple of weeks but you can't be giving penalties away when they've got boys like Dan Biggar and Sam Davies in their team.
"We'll be tough on ourselves now. We've got another derby in four days so we've got to get our heads on for that and make sure we turn up."

Ecuele Manga, 27, last featured for Cardiff in their 2-1 defeat at Fulham.
"It might be the case that he has malaria. He is out of hospital and will be commencing training later this week," manager Russell Slade told BBC Radio Wales.
"That is good news, having suffered a virus of that kind of capacity. We see it all at Cardiff City."

The boat is understood to have capsized in the Durris area, at Craiglug.
The Scottish Fire and Rescue Service initially said one of the three - believed to be teenagers - made it ashore, and efforts were being made to reach the other two who were stranded on an island in the river.
They were later rescued by boat.
The alert was raised shortly after 13:45.

A bounceback for US shares, a further recovery in China and a stellar performance by Japanese shares helped the benchmark FTSE 100 index to close 82.91 points or 1.35% up at 6,229.01.
Revised growth figures for the eurozone on Tuesday also underpinned confidence.
Ryanair was a strong performer, up 5.2%, after it said profits would be 25% higher than thought.
Broker Hargreaves Lansdown's shares were up 7% after its results and Barratt Developments shares were 0.2% higher after an initial 2% rise. It earlier reported profits up 45%.
Foxtons estate agents were another good gainer, rising 3.75% after an upgrade.
On the currency markets, the pound was down 0.2% against the dollar at $1.5366 but was up 0.2% against the euro to â‚¬1.3774.
Police have used a "covert lorry" to spy on drivers using their phones.
[NEXT_CONCEPT]
Scarlets captain Ken Owens says they can bounce back from their derby defeat by west Wales rivals Ospreys - just like they recovered from losing their first three games of the season.
[NEXT_CONCEPT]
Cardiff City centre-back Bruno Ecuele Manga is recovering from malaria having been released from hospital.
[NEXT_CONCEPT]
Three girls who sparked a rescue effort in the River Dee in Aberdeenshire after reports of a boat getting into difficulties are all safe and well.
[NEXT_CONCEPT]
(Close): London's leading shares ended the day in positive territory as global investors regained confidence.