CHIPS star (and writer and director) Dax Shepard said his love of the old TV show was tied to his lifelong love of anything with wheels and motors.

For Shepard, watching stars Larry Wilcox and Eric Estrada weaving their motorcycles through L.A. traffic offered a kind of "car porn," the chance to see now-vintage cars in their natural 1970s habitat.

"I'm the Larry Flynt of car porn," said Shepard, who grew up near Detroit in a GM family, who worked for the company himself in his teens and 20s, and whose first directing job (Hit & Run) was a tribute to the muscle-car movies of the 1970s.

He also has a degree in anthropology, which gives him a unique window into the startling changes in American culture relative to the automobile -- Shepard's generation of car nuts is giving way to a generation, weaned on web-based chauffeurs, eagerly looking forward to cars that drive themselves.

"I have so many friends who are just beyond excited to have their Tesla drive them somewhere. My feeling is, if you're going to be in the car, you should at least have the pleasure of driving the thing," said Shepard, who stopped in Philadelphia with costar Michael Pena to promote the movie, opening Friday.

Pena pointed to the practical advantages of self-driving cars.

"You can get work done."

Shepherd was unconvinced.

"But you won't. You'll check your Twitter 25 times, or go on Instagram and get really jealous about somebody else's vacation."

Shepard, who grew up on cars and movies, said cars have been an essential part of the language of film -- every bit as important to the iconography of freedom and independence as the horse was to the western.

If cars have been used in cinema as a symbol of freedom and independence, what would self-driving cars symbolize?

"Its weird to me that kids these days aren't counting down the day until they get their license. That blows my mind. I was driving underage. I was sneaking the car out. It was all I cared about. Every time I had a break, I was planning a road trip. The idea of being this completely autonomous entity, that I could go anywhere, that is like having a superpower."

He has tried for years to explain this to his wife, Kristen Bell, but she didn't get it -- until she saw CHIPS.

"She said, 'I can't believe you made me care about motorcycles.  I get it now. You're going up and down staircases, you're jumping over things, you're going super-fast, you're catching the bad guys, it makes you a superhero.' I was pleased with that."

Pena, whose brother is a police officer, admired the original TV show for different reasons.

"I just love the story of two guys who are friends. And as a Latin guy, I like that there is a Latin guy who's part of the group, doing some good. Not getting arrested, but being a good cop. There's something cool about that."

Danny Boyle on 'T2 Trainspotting'

Movies have been preoccupied recently with time and aging -- Richard Linklater with his Sunrise trilogy and Boyhood, even Logan with its superhero-in-winter premise.

The latest in that vein (pardon the pun) is T2 Trainspotting, a chance for Danny Boyle to revisit his 1997 surprise smash, at the time a galvanizing rebel yell for U.K. youth, seen through the experiences of four hedonistic Scots friends (Ewan McGregor, Robert Carlyle, Jonny Lee Miller, Ewan Bremner).

All key members of the original cast were game for a reunion, even after Boyle told them how merciless the sequel would be.

"We told them, 'Look, we're literally going to be juxtaposing you with the original incarnations of you, right there on screen. That will be cruel for you,'" said Boyle, who weaves snippets from the original into T2, contrasting the chest-puffing of youth with the sagged shoulders of middle age.

T2, which opened Friday, wades remorselessly into the subject of fortysomething disappointment. The four men didn't have much in the original aside from friendship, and in the embittered T2, they don't even have that. The plot has them settling old scores.

"There is a place for carelessness and rebelliousness, and that place is youth. But you keep going, and by the time you get to your 40s, that is gone, and you've lived, and gotten married, and fathered children, and suffered disappointments. [T2] is about that, and about the process of atonement."

Knitting together images of the characters, young and old, makes the point in a unique way, Boyle said.

"I think movies, of all of the art forms, are about time. Someone has said, and it's true, that when you're editing, you're really doing two things -- you slow time down, or you speed it up. In more extreme circumstances," Boyle said, "you can freeze time, unlock time, or imagine future time."

Time, he said, also frames the interaction between director and audience.

"Part of the contract with the audience, you ask for 90 minutes or two hours of their time, and they give it you, and you give them in return an interpretation of time. No other art form can do that, play with time in front of you like that. No wonder movies turn to time as a subject."