Symbolism, Imagery, Allegory
You're 16…what's the first thing you do? You get your driver's license. Freedom—that's what the car means to you. That's what the car means to Mrs. Sen.
The only difference? You're probably not freaked out by this symbol of American independence and mobility (your parents, on the other hand, probably are).
Why is Mrs. Sen so reluctant to drive? First, there's the whole issue of focus. It's hard to do, especially if you're a distracted driver, which Mrs. Sen is—"continuously distracted" (MS 39) in fact.
And then there's the whole business of merging into oncoming traffic:
Each time they approached the grove of pine trees where the asphalt loop met the main road, she leaned forward, pinning all her weight against the brake as cars hurtled past. It was a narrow road painted with a solid yellow stripe, with one lane of traffic in either direction.
"Impossible, Eliot. How can I go there?"
"You need to wait until no one's coming."
"Why will not anybody slow down?" (MS 39-42)
Pretty scary, if you look at it from a newbie driver's perspective. Maybe even enough to make your "knuckles pale…wrists tremble…English falter" (MS 45) like Mrs. Sen.
Okay, sure, you're thinking, driving can be dangerous, but what's the "larger meaning" behind Mrs. Sen's fear? It turns out that, where she comes from, a woman of her class doesn't need to be independent in the same way (she, for example, had a chauffeur in India).
Moreover, driving in America is just another form of isolation. As Mrs. Sen tells Eliot after one of their driving practice sessions, "Everyone, this people, too much in their world" (MS 46). And, if you think about it, she's not exactly wrong. What do you do, after all, when you're in your car? Roll your windows up and listen to music, probably.
The image of Mrs. Sen waiting anxiously as she watches the American drivers go whizzing by is a powerful one. She has no idea how to merge into the traffic, to "merge" into this new fast-paced culture.