The largest such system I'm aware of is slugging in the DC area (particularly along the 95/395 corridor to Pentagon/downtown): at various parking lots, a driver pulls up to a line of people, says they have 3 slots and is heading to the Pentagon (say), and 3 people pile in and get to ride the HOV to the Pentagon.

It's entirely free, almost entirely grassroots (governments occasionally ask that the pick-ups/drop-offs move slightly), and remarkably safe (1 known incident in >30 years). Having grown up in the area, I was surprised when I casually made reference to it to someone not in the area and they had no idea what I was talking about.

Having never spent more than a few days in DC, the only reason I know about slugging is because of "Slugline" in House of Cards.

I've been riding the Casual Carpool for the last 6 years. Love it! The reason drivers don't care about "revenue" is that they are driving across the bridge anyway and care more about the time than money. Another way to think about it is the 30 minutes saved by picking up riders and getting into the carpool lane is payment enough. Also explains the reason why riding back to east bay is not "successful". It isn't particularly faster nor as convenient.

I always wondered why they don't toll the reverse direction as well.

Aren't most tolls everywhere just in one direction? That way, half the number of toll booths are needed compared to both directions (before FastTrak, etc each lane required a human cashier)

I don't know; I'm no expert on typical tollway designs. I've certainly seen turnpikes that are tolled both ways.

Anyway the number of cars queued up to cross the bridge to the east in the afternoon strongly suggests that road is underpriced.

By implementing another toll gates, they might actually worsen the traffic jam. When I cross the Bay Bridge, i see lines upto the toll booths, and after them, it's usually clear.

Sure if the cost is based on mileage then there would have to be tolls on both sides

They charge you for the privilege to visit SF, not to leave it.

Well that doesn't make any sense either, because there is no toll at the southern entrances to SF on 101 and 280.

I'm not looking for an answer here because I know the answer. The answer is that car drivers are the most self-entitled bunch of externalists the world has ever seen. If there was any sense in this system the toll at the existing toll plaza on the Bay Bridge would have been raised until congestion disappears, but that hasn't happened. On the other hand BART fares are indexed to inflation, because only the riff-raff ride transit.

#2 is the kind of system that's ripe for "disruption" (or whatever your favorite buzzword is for this). Is the answer specifically this app? Maybe not, but "pretty nice systems" don't tend to involve "usually", "chip in", or "common" (not to pick on your specific language, I just mean the "hidden" knowledge and customs that come with informal, organic systems).

It's that informal and inconsistent group knowledge that gets turned into an app, which formalizes the informal parts, removes the barrier to entry (knowing about the informalities in the first place), and (should) build protections in to ensure conformity to the now established system (payment, insurance, etc).

Casual carpool does not solve the first/last mile problem, though. Lyft Carpool seems to be door-to-door.

Fair but OTOH I don't mind walking 5 minutes for a free ride into the city.

I don't think the first and last mile problem applies to people living within a 5-minute walk from a casual-carpool pickup location. Most people would probably choose Lyft over casual carpool if they lived, say, 20 or more minutes from their nearest casual carpool pickup.