Ray Bradbury was often accused of being a Luddite: that is to say, someone with a knee-jerk hostility towards new technology. But this was always an unfair criticism, as Bradbury was never concerned with criticizing technology, per se, but rather how it is used and abused by humans, especially by those in a position of authority.

The dystopian society depicted in Bradbury's short story "The Pedestrian" is technologically advanced, and this in itself is not a problem. However, technology has been utilized by the authorities to impose a mindless conformity on the general population, reinforced by the serving up of mindless dreck on TV, which the masses gleefully consume every night.

In such a technologically driven society, the tail wags the dog; instead of technology serving the needs of humans, humans serve the needs of technology. Among other things, this means that there's no longer any call for books and magazines, which renders writers like Leonard Mead virtually redundant.

In a society like this, technology has crowded out human imagination, the very stuff of which books and magazines are made. As such, individuals like Mead are regarded with suspicion; at best, they are eccentrics, at worst, potential dissidents. Either way, they do not belong in a society in which technology serves as a tool of political repression.

A writer no longer writes because books and magazines no longer sell. Television has replaced books and any other source of recreation or entertainment. No one even goes out for evening walk and if somebody does it’s thought to be weird.

The world has become technology-driven. Individualism has no place here. One evening a fully automated patrol car discovers the narrator walking all alone and learns that he’s got no wife or friends. The computerized car decides that the narrator’s activities are abnormal. His proper place would be “the Psychiatric Center for Research on Regressive Tendencies.”

Thus, one of the central themes of Ray’s story is the dehumanization of the human society ensued by the technological development. In this advanced human society, the houses are “tomblike” where people sit before their television sets “like the dead.”

Like machines people work during the day time and once back home, glue themselves to the TV.

During the day it was a thunderous surge of cars, the gas stations open, a great insect rustling and a ceaseless jockeying for position as the scarab beetles, a faint incense puttering from their exhausts, skimmed homeward to the far directions.

The citizens of this highly civilized world peep out of their windows and flash lights to express amazement seeing the narrator out on evening walk all alone.

Disdain for individualism and loneliness are other important themes in the story. Individualism actually has no place in this greatly developed human society. It may cause utter loneliness.

The narrator, a man with individual thoughts and opinions, has no wife, family or friends. "Nobody wanted me,” he says.  He is a misfit in this society and as because he doesn't belong to this place, he is taken to the laboratory. Research on him may make the writer worthy of at least something and possibly lead to further human progress.  

The story is about the degeneration of human society in a highly developed and civilized society driven by technology.

Ray Bradbury was clearly prescient about some of the looming problems of the future. His theme in "The Pedestrian" is that a society in which technology dominates lives leads to conformity, lack of imagination, and individualism. The lone individual, the writer who no longer has an audience, walks the streets alone, isolated from the homes that are dark inside except from the single light of televisions, "a loud yellow [the color of evil]illumination," which mesmerize the viewers into complacent, unthinking lives. Leonard Mead sneaks down sidewalks overgrown with weeds because of disuse, peaking around corners for the inanimate police car that picks up vagrants, asking no one "Are you there?" longing for human communication, the food of the heart of man. 

Instead, he is halted just as he approaches his own house, told to raise his hands as though he is in the act of a crime. When Mead must admit that he has not written anything in some time (since no one reads), he is ordered into the car and the vehicle heads "To the Psychiatric for Research for Regressive Tendencies." 

To me, the theme of this story is that TV (and I think technology in general) can destroy a society.  I think that this is a fairly typical Bradbury theme and can also be seen in stories like "The Veldt."

In this society, human relations no longer exist and neither does freedom.  Everyone always just stays home watching TV.  Leonard Mead, for example, does not have the freedom to go out and do what he wants to do.  He gets picked up by the police because he is not doing what is expected.

This shows that individuality has been pretty much destroyed by the prevalence of TV in this society.