Williams test driver Susie Wolff is to retire from motorsport.
The Scot - the first woman to take part in a grand prix weekend for more than 20 years - believes her aim of racing in Formula 1 "isn't going to happen".
"It was a decision I made at the end of the summer. There was very little opportunity to carry on in Formula 1," the 32-year-old told BBC Breakfast.
"My goal was to get on to the starting grid and that didn't look achievable. So I had to call it a day."
She added: "I always said that as soon as I couldn't get any further I would stop and that time has come."
Wolff will make one more appearance as a racing driver - in the Race of Champions in London's Olympic Stadium on 20-21 November, racing for Scotland alongside former F1 driver and BBC F1 co-commentator David Coulthard.
She started working with Williams in 2012, after racing for seven years in the German Touring Car Championship.
An initial trial in the car developed into a full-time test and development role and she took part in four practice sessions at grands prix over the past two seasons, alongside work in test sessions and in the team's simulator.
But her decision to retire was partly influenced by an incident in March, when her team ruled out the possibility of using her as racing cover for Valtteri Bottas in Malaysia.
"I don't think it was the pivotal moment, but it was one of the moments where I could just see it getting harder and harder," she said.
"But I said to myself 'is this ever going to happen?' It was the harsh reality that the dream wasn't going to come true."
Williams deputy team principal Claire Williams said: "It has been a pleasure to work with Susie over the years and see her develop as a driver within the team.
"Her feedback and knowledge of the car has been an important part of our recent development and we will be sorry to see her go."
Women 'can race in F1'
As the only female racing driver with close links to F1, Wolff became a figurehead.
"I do believe a woman can compete at that level," she said.
"I showed that in testing. I don't think it will happen very soon, but I will definitely make sure I help the next generation.
"My progression into F1 came to represent so much more than a racing driver simply trying to reach the pinnacle of the sport.
"It was also the hope that finally there may again be a female on the starting grid. I rode the wave, was energised by all the support and fought hard. There were those who wanted it to happen. Those who didn't."
Wolff said she had given her all in her attempt to secure a race seat.
She added: "We have two issues - not enough young girls starting in karting at a young age and no clear role model. Sometimes you just have to see it to believe it."
Top Gear next for Wolff?
Wolff says she wants to try to help the next generation of women make it in motorsport.
"I want to give something back," she said as she prepares to link up with the Motor Sports Association, the UK motorsport authority.
"We will launch a new initiative aimed at celebrating the woman succeeding in motorsport on and off the track now, plus highlighting to the next generation that motorsport is an option for them.
"I dared to be different, I want to inspire others to do the same."
Wolff, who is married to the boss of the world champion Mercedes F1 team Toto Wolff, says she is unlikely to continue to have an active role in the sport.
"I will attend some races as Toto's wife and a friend of the Williams team but I don't want to be absorbed by F1 like I am now," she told BBC Sport.
"I want to leave completely and give myself room and space to move on to something else. I have a great platform behind me and I will use it in a positive way.
"I'm still young and I want to go on and find that next passion in life so I can wake up every day with a purpose."
Wolff has been linked with taking up a presenting position on the BBC motoring show Top Gear.
When asked if it was something she would be keen on, she told BBC Radio 5 live: "Yes, who wouldn't like to do Top Gear?
"I've had some discussions. There is no story just now."