Terrie Kirby is reported to have been celebrating the milestone when she died along with her three friends, Ryan Beal and Brandon Brown, both 20, and Alexandra Binns, 18.
They died when their quad bike was hit from behind by a Nissan 350Z on the A6201 between Upton and Hemsworth in West Yorkshire at around 12.30 on Sunday morning.
Three died at the scene while one of the men died in hospital from his injuries. They are all believed to be from the Upton area.
Two men aged 21 and 22 who were in the car were arrested on suspicion of dangerous driving and were later bailed pending further inquiries.
Friends and family members spoke of their shock and heartbreak on social media, and one said Terrie had died on her birthday.
Ashleigh Lynch wrote on Facebook: “I don’t actually know what to do with myself. Absolutely wounded, my heart’s actually melting. Why does it have to the best ones?
“My best friend out of it all. And on her 16th birthday. You’re my angel. My beautiful Alexandra, Beal, Bran and Drea will show you how to have a good time.”
Jeorgia Lynch added: “Can’t believe it, doesn’t seem true. Going to miss you Ryan Beal, Terrie Lynch. Fly high, don’t party too hard up there, beautiful angels. Love you Alexandra Binns, Brandon Brown, all too young, taken too soon.”
Others also remembered Terrie as a “beautiful young lass”.
Daniel Haywood said: “Gunna miss this beautiful face. Love you so much Terrie. Fly high my darling, good night and god bless, sleep tight my little beauty. Until we meet again.”
Liv Parsons added: “Rest in paradise beautiful, love you loads,” while Bronte Pretty posted a photograph of herself with Ms Binns to her Facebook page, saying: “My best friend, my rock, my sister. I love you Alexandra Binns, until we meet again.”
She added: “Words can’t describe the pain I’m feeling, heartbroken doesn’t come close.”
Anya Jones, a friend of Alexandra Binns, wrote: “What a beautiful girl you had so much going for you. RIP. Thoughts go to your family right now.”
Adam Philips, a friend of Ryan Beal, said: “Can’t believe it. RIP bud.”
West Yorkshire Police said the quad bike was unregistered when it was being driven.
Mr Beal, who according to his Facebook profile was a fitter for windows firm Safestyle UK and had gone to Minsthorpe Community College, posted a photograph of a green Yamaha quad bike to the social media page earlier this month.
The country road where the collision happened was still closed today, and rush hour traffic was being diverted away from the scene.
Police tape was strung across the grass verge and tied to barricades and road and footpath closed signs.
Beyond the cordon, a single police officer stood next to his van, guarding the entrance to the crash site, which was shrouded in fog.
Specialist officers are supporting the families of those involved and police are appealing for anyone who witnessed the incident or saw an unregistered quad bike or the bronze Nissan car being driven around the Hemsworth area on Saturday evening.
Police believe the Nissan was travelling towards Hemsworth on the A6201 when it was in “collision with the rear of the quad bike”.
Det Chf Insp Richard Holmes, of the Homicide and Major Enquiry Team, renewed a police appeal for witnesses when he spoke at a press conference at the scene of the tragedy this afternoon.
He said: “A number of witnesses have told police that a short time before the collision, the Nissan 350Z was seen parked up nearby, along with a number of other cars. Police urgently need to speak to any occupants of those cars and ask them to contact the Major Collision and Enquiry Team on 101.
“We also now know from witnesses that the quad bike was in and around Hemsworth town centre about an hour before the collision and also ask any witnesses who may have seen it to come forward.
“Officers are continuing their meticulous enquiries at the scene and it is vital that we speak to anyone who may be able to provide information, no matter how small.
“This is a tragedy for the families of those involved and a huge shock to the whole community.”