Third seed Stefanos Tsitsipas beat Filip Krajinovic 3-6 6-4 6-4 to book a semi-final with nine-time champion Roger Federer at the Swiss Indoors.
The 21-year-old World number seven served 12 aces and beat the 46th-ranked Serbian in an hour and 53 minutes.
Fourth seed Roberto Bautista Agut’s hopes of reaching next month’s ATP finals were dented by a 6-3 3-6 6-3 defeat against American Reilly Opelka.
World number 37 Opelka served 31 aces in his win in an hour and 33 minutes.
With the top eight players qualifying for the O2 Arena from 10-17 November, ninth-placed Bautista-Agut was trying to keep pace with eighth-ranked Matteo Berrettini, but the Italian reached the semi-finals of the Erste Bank Open in Vienna to increase his lead to 130 points.
Federer, who dropped only six games in wins over Peter Gojowczyk and Radu Albot, had a walkover into the last four after fellow Swiss Stan Wawrinka withdrew because of a back injury.
France is bringing in new rules for the use of electric scooters following hundreds of incidents involving the vehicles, including several deaths.
From Saturday, riders will be required to be at least 12 and will not be able to ride their scooter on the pavement.
The two-wheeled vehicles’ top speed will also be capped by next year.
E-scooters, which can travel at more than 50km/h (30mph), are growing in popularity, in part because of their low environmental impact.
Junior Transport Minister Jean-Baptiste Djebbari said in a statement the new rules would encourage “more responsible use… and restore a sense of tranquillity for pedestrians, in particular the most vulnerable: the elderly, children and handicapped people“.
But Hamilton rejected the criticisms and said everyone could do more to protect the environment.
“It is something over time I have become more and more aware of,” he said. “It is not a quick fix. It takes time to understand the implications. I would feel I wasn’t doing anything positive if I didn’t mention it.
“It’s important to be able to be open and not hold things in. I’m always very open and transparent with my feelings, whether people like it or not.”
Speaking on the eve of the Mexican Grand Prix weekend, where he has the possibility to clinch his sixth World title, Hamilton gave a long list of efforts he was making in his own life to protect the planet.
These included trying to make sure he is carbon-neutral by the end of the year, forbidding his office or anyone in his household from buying plastics, selling his private plane, travelling less, using an electric car and encouraging Mercedes – both the F1 team and the car company – to make relevant changes.
He also emphasised that the turbo hybrid engines introduced into F1 in 2014 use a third less fuel than previously.
He was backed by Ferrari driver Sebastian Vettel and other drivers in the official news conference in Mexico City on Thursday.
Vettel said: “It is very difficult for us to have acceptance from the outside because we don’t have the smallest [carbon] footprint. The races are around the World and we do have to travel.
“But I feel F1 should do more. It is a worldwide operating platform and we should send a more positive message.
“Everyone can do something, contribute a little bit and if the whole World acted like that it would make a huge difference. It is inevitable change is coming and hopefully sooner rather than later.”
Red Bull’s Alexander Albon added: “What Lewis said was really good. Just because we are in F1 doesn’t mean we can’t care about the environment.”
Hamilton doubts he will clinch title in Mexico
Hamilton played down his chances of sealing the championship in Mexico this weekend.
To do so, he needs to score 14 points more than team-mate Valtteri Bottas, the only driver who has the mathematical possibility to overhaul Hamilton’s points score.
“I don’t think in the season I have finished 14 points ahead of Valtteri at any point,” he said. “It may have been one race, Valtteri has been strong all year and I expect him to be strong this race as well.”
The only time Hamilton has done so was in the Hungarian Grand Prix in early August, when he won and Bottas finished eighth after damaging his car in a collision with Ferrari’s Charles Leclerc on the first lap.
Hamilton expects Ferrari to be strong favourites in Mexico because the track rewards straight-line speed, where the Italian cars have a significant advantage over Mercedes.
“We go into the weekend knowing Ferrari are massively quick on the straights and they are a powerful part of this circuit,” he said.
“I don’t know when we’ll be getting another pole but it is not all about qualifying. It’s about getting the car ready for the race, this track bodes well for the Ferrari and Red Bulls but maybe we will have a better chance than in the past.”
How Hamilton can win the title in Mexico
Win plus fastest lap with Bottas lower than third
Win with Bottas lower than fourth
Second plus fastest lap with Bottas lower than seventh
Second with Bottas lower than seventh
Second with Bottas lower than eighth if Bottas sets fastest lap
Third and fastest lap with Bottas lower than eighth