The message of Ray Bradbury's "The Pedestrian" is a concern that technology desensitizes Americans and causes them to become alienated from others. 

When Leonard Mead walks at night in sneakers so that no one will hear him and call the police,

...it was not unequal to walking through a graveyard where only the faintest glimmers of firefly light appeared in flickers behind the windows. Sudden gray phantoms seemed to manifest upon inner room walls....

Mead experiences an isolation that, as a writer, he finds disturbing. No longer are there people with whom he can converse and exchange ideas, no longer are there people with whom he can share feelings or enjoy company. In addition, he may well be worried about his livelihood, because when the automated police car stops him, Mead is asked what his profession is, and he replies, "I guess you'd call me a writer." The car responds, "No profession," and Mead observes "You might say that" because he has not written in years. People no longer read books or magazines. Instead, they sit in their dimly lit "tomb-like houses" at night, passively watching television that emits a small light that touches their faces. Television entertains them, but "never really touch[es] them" as the written word does because it is the expression of the human experience that unites people to one another rather than isolating them in their lifeless homes. 

Clearly, Bradbury is concerned that, with the distractions of technology, people become desensitized and removed from the enriching human experience contained in the written word.

What social trends does Ray Bradbury observe and see as problems for society?

The story presents an exaggerated portrait of an imagined future city. It may seem like a far-fetched imagination of an artist; nevertheless, it’s not merely an expression of fanciful ideas. Actually, the story draws its material from the popular social trends of the author Ray Bradbury's time, and merely, articulates his anxiety over them. 

First and foremost, the story raises concern about man’s growing addiction to television. The story was first published in 1951. In the 1950s and 1960s, television was becoming tremendously popular. “Many critics have dubbed the 1950s as the Golden Age of Television.” People would spend hours sitting before their television sets day and night.

In "The Pedestrian," nobody in the “city of three million” comes out of their “tomb-like” homes for social gathering or evening walk. Everybody sits glued to TV screens switching channels. For over ten years, the speaker hasn't found any human while he’s out on his regular evening or morning walk. He says, 

In ten years of walking by night or day, for thousands of miles, he had never met another person walking, not once in all that time.

Before TV became popular, reading was one of the most common sources of entertainment. Reading books and journals was being replaced by sitting before television. This was another changing trend the author was observing all around.

In the story, nobody reads anymore. Writers are regarded as persons with “no profession.” Bradbury expresses his fears over the society turning philistine with man's growing love for TV.

Another trend taken up in the story is man’s increasing dependence on machines. With innovations in the fields of science and technology, machines were penetrating in all spheres of human life. The author expresses his concern about man’s growing enslavement to machines.

The patrolling police car that finds the lonely speaker walking at night is fully automated. There’s no human police inside. Its metallic voice won't allow the pedestrian to speak even a word that’s not asked by it.

"Nobody wanted me," said Leonard Mead with a smile.

"Don't speak unless you're spoken to!" (The police car said.)

Bradbury seems worried over the long-term impact of man's growing obsession with TV and technology. He fears it might lead to the degeneration of human society. It might make man machine-like, devoid of any creativity, sensitivity or imagination. He fears, in the future, man might no more crave for aesthetic pleasure. Besides, it would detach him from the world of nature.

So, we see that the story picks up the popular trends of the day, and asserts Bradbury’s apprehensions in the wake of the changing social values. 

What social trends does Ray Bradbury observe and see as problems for society?

Great question.

In this classic story, Bradbury identifies several intersecting social trends. These come together to form tremendous problems. 

One is simply conformity with mass movements. The pedestrian is the only person who acts the way he does. This isn't just rare in this story. It is literally criminal.

A second trend is people sitting and watching television. All the houses the pedestrian passes are full of people sitting and watching television. It almost medicates them against action.

A third and closely related trend is using broadcast media instead of the written word.

All of these combine to do two things that Bradbury hates: destroy community and distance people from nature. Look at the familiar love for the town and the night expressed in the first few lines of the story. The pedestrian is the only one who ever experiences those now. Community and nature are lost to humanity.