Besides, very few things need a hechsher. Mostly meats and certain cheeses and wines. If things did need Hechsherim, we would have real problems, because most of those are not in the least reliable.

With regards to the bus in an Eruv… First, I recommend everyone read the Torah Talk entry regarding Boats, Buses, Trains, and Planes. https://kashrut.org/project/can-you-ride-a-train-bus-plane-or-boat-on-shabbat/
Second in response to your questions:
Using a prepaid card works. Going on the bus is perfectly fine. passing it through the scanner is not any Melachah that I’m aware of, so it is also fine. Stopping the bus at a stop where he is not going to stop except for you… is ok, because again there is no Melachah that he is doing. Even if driving the bus is Havaarah (Like Lighting a Fire), however stopping the bus is not Mechabeh, because Mechabeh needs a Pesilah (Petilah = Wick) in order to be a Melachah.

So in summation…Yes, Yes, Yes, Yes, and Yes. Enjoy

The key difference between wheat-based glucose and products like vinegar or whiskey lies in both the process and the halachic principles of ta’arovot—mixtures involving potentially problematic ingredients.

In halacha, when a non-kosher (or in this case, chametz-derived) ingredient is mixed into a food, the primary question becomes whether the original forbidden substance is still discernible in taste. This is where the concept of batel beshishim—nullification when the forbidden substance is less than 1/60th of the total—comes in.

Whiskey is often made entirely from fermented grain, possibly barley or wheat. Since the grain is the essence of the product, and the resulting alcohol is a direct product of fermentation (not distillation from non-chametz sources), we cannot assume any bitul without precise knowledge of the composition—which we rarely have from manufacturers.

Vinegar is more nuanced. If vinegar is listed as the third ingredient or later in a product, we know mathematically that its volume is small enough that any chametz content (such as from wheat-based alcohol) would be batel beshishim. But when vinegar is listed among the first two ingredients—such as in salad dressings—it may not be nullified, and we treat it more strictly.

Glucose syrup, on the other hand, is an ingredient used in extremely small quantities—especially in processed foods where it’s often one of many sweeteners or stabilizers. Even when it is derived from wheat, the wheat starch undergoes a chemical transformation that renders it unrecognizable in both substance and flavor. Furthermore, the actual proportion of any wheat that may remain is negligible—automatically falling well below the 1/60 threshold. That’s why glucose syrup, even if wheat-based, does not pose a chametz concern in practical halacha.

In summary, the halachic leniency for glucose syrup is grounded both in its chemical transformation and its minimal volume, while products like whiskey or vinegar require closer scrutiny due to their nature, source, and usage in larger concentrations.

Years ago, we did a test on ovens. We took water, brought it to a full boil on the fire—steam pouring out everywhere—and then threw it into a preheated oven. What happened? The steam disappeared immediately. The water stayed hot and continued boiling, but there was no visible zeiah (steam) inside the oven.

Why? Because of how modern ovens are built. In our ovens, the steam gets burned out and dissipates into the air inside the chamber. That means there’s no halachic zeiah that would transfer taste. Yes, the Gemara talks about a tanur and a kirayim, and we often translate those as “oven,” but halachah doesn’t work by simply translating terms and transplanting halachos without understanding the differences in design and function. Our ovens are fundamentally different.

So what’s the halachic bottom line?
You can technically cook meat and milk in the same oven—even at the same time—and there’s no transfer of taste or issur. Likewise, you can cook kosher and non-kosher in the same oven simultaneously, and one does not affect the other, unless there is actual physical transfer—like liquid from one dish spilling into another. So yes, keep your eyes open. If your salmon is leaking onto the food underneath it, that’s a real issue. But absent that, there’s nothing to worry about.

As for the pizza question:
The heter isn’t noten tam lifgam. Pepperoni, for example, isn’t lifgam—it’s flavorful. But that’s not the point. When you order a vegetarian slice in a pizza shop, especially in Western countries, they won’t put meat on it. It’s not about kashrus at that point—it’s about liability. No one’s going to risk a lawsuit or bad press. So if you walk in and ask, “Is this vegetarian?” and they say yes, you can rely on that—often more confidently than in a kosher store.

In short:
• Modern ovens don’t transmit taste via steam (zeiah) because it gets destroyed inside the oven.
• Therefore, halachically, you can use a non-kosher oven for kosher food as long as there is no direct contact or liquid transfer.
• And when ordering vegetarian in a non-kosher store, you can rely on what they tell you—especially when it comes to meat—not because the pepperoni is lifgam, but because it’s not going near your slice in the first place.