The offender, who was granted name suppression, was driving alone heading north.
The weather was fine with good visibility and the road surface was dry.
Witnesses reported seeing the offender's vehicle weaving into the grass verge, correcting, then crossing the centre line at least three times.
One witness said the offender was "completely in the opposite lane" and another said the vehicle was moving into the lane "very quickly".
On a straight stretch, 300m north of East Rd intersection, the offender hit Gladding's Nissan.
Gladding died at the scene, aged 60, and his tangi was held at Mataarae Marae in the days after.
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The offender spent a month in hospital, and did not recall the crash, but claimed he had most likely used the drugs a couple of days prior.
In the Rotorua District Court this afternoon, Gladding's family members hugged, rubbed each other's backs, sobbed and wiped their eyes and glasses as they read their victim impact statements between long pauses.
Maria Gladding was married to Rolly for 15 years before she was widowed.
She called her husband's phone non-stop, for half an hour, when she first heard of a crash nearby.
When Maria was told of Rolly's death, her "life came crashing down".
"The whole experience was a blur as I later sat at the dining table with my eyes shut, hoping when they opened there would not be a horrible, horrible nightmare."
When Maria went to see her husband's body at hospital, her friend had to hold her up for five minutes as they walked to the basement.
"There he was. My husband, my soulmate, my protector, my life, my everything - lying on a hospital bed covered with a white sheet. I did not sleep that night."
She was later prescribed sleeping pills, and would bury herself in Rolly's favourite pillow wearing his favourite shirt, to get to sleep.
Maria said since the crash she had had no control over her emotions, had lost confidence, and had been getting counselling to find "a new normal".
"I no longer have his income for bills that still need to be paid. I am often scared in my own house... and living in a small rural community also means rumours can travel like wildfire."
She said her whānau always knew when Rolly was around, because of his "big barrelling laugh".
"The day he was killed, we lost our identity. Our happiness and laughter was all sucked out."
Maria's son, and Rolly's stepson Andrew said the impact had been "horrendous" and had caused "lifelong pain".
In court, Andrew turned from Judge Philip Cooper, to face the offender as he spoke.
He held eye contact for long periods of time with the man and said: "Nothing you say or do can change the sentence you have given my family."
"Eventually, you will get to go home to your family, my stepdad won't."
A statement submitted by Gladding's brother Ross said he had felt Rolly's death strongly.
"We would often speak on the phone at 4am in the morning... Talking about anything."
He said Rolly was the third person in the family to die in a road accident.
Defence counsel Ngaroma Tahana argued fatigue was the main factor in the crash, not the drugs or alcohol in her client's system.
The offender had one previous conviction, for drunk driving.
Judge Cooper addressed the Gladding family in te reo, before addressing the offender's family in English.
"There are no winners in a case like this, everyone is a victim, even the defendant. I don't say that to minimise his behaviour."
The offender showed little emotion as he was sentenced to three years in prison, and disqualified from driving for three years.
