6 ms·

Almost before anyone cites supply/demand: > the company (said) two salt and plow trucks were working on the southbound Express Lanes on I-495 and I-95, causing

by j1vms 10y ago

Almost before anyone cites supply/demand: > the company (said) two salt and plow trucks were working on the southbound Express Lanes on I-495 and I-95, causing traffic to slow and increasing the toll on those lanes. So no one was going anywhere because of salting and plowing yet the tolls were unaffected and they increased the premium - which would have changed... nothing.

pavel_lishin 10y ago
So the problem here is more of a faulty algorithm?
- denzil_correa 10y ago
  You wouldn't know, you'd have to audit the algorithm to reveal the details.
- Vivtek 10y ago
  Less a "faulty algorithm" and more a moral hazard. The intent of the rules is to limit usage during periods of congestion not caused by the road operators themselves. The distinction is that human actors are not moral-free mechanisms.
  - deleted 10y ago
    [deleted]
totally 10y ago
Right, traffic density increased without a corresponding increase in throughput.
6DM 10y ago
Honestly, I only saw a few flurries. I think everyone saw that and hopped on the express lanes. The day before a little rain fell and there were accidents everywhere. Guessing it was fresh on our collective minds. I passed a lot of cars in the express lanes on my way home. Cringing at the though of what car accidents lay ahead, but everything was clear.
aninhumer 10y ago
Arguably though, if the capacity of the road is reduced, then charging more for what remains is supply and demand, right?
- denzil_correa 10y ago
  In that case, one could charge $100 right? The capacity of the road is reduced then as well.
  - aninhumer 10y ago
    No, I'm not saying the price increase is reducing capacity. I'm saying the trucks are reducing capacity (i.e. supply) and so the price is rising in response.
    - denzil_correa 10y ago
      > I'm saying the trucks are reducing capacity (i.e. supply) Source?
      - aninhumer 10y ago
        The comment I was originally replying to? >> the company (said) two salt and plow trucks were working on the southbound Express Lanes on I-495 and I-95, causing traffic to slow
        denzil_correa 10y ago
        Now, I go back to my original question : Why is $30 the price that will do so? It could be $5 or $100.
        aninhumer 10y ago
        Well I don't know exactly how their algorithm works, but I'd guess they keep track of average travel times by scanning licence plates, and then raise prices when they go below the target speed, and lower them again when speeds increase?
claydiffrient 10y ago
I think perhaps it worked as intended right? The goal seems to be to keep traffic free flowing in the lane. > Tolls for the Express Lanes are dynamic, meaning they change periodically based on real-time traffic conditions to keep the Lanes free-flowing. > However, rates may rise significantly above the typical range for periods of time in the event of unusually heavy congestion or a specific event like a traffic accident or lane(s) closure. So because the trucks were slowing things down the price raised deterring more vehicles from entering and slowing this down more. It makes sense to me. ¯\_(ツ)_/¯
snarf21 10y ago
Maybe I misread this but my understanding is that the algorithm is intended to have all lanes have the same flow rate. If one lane is slow, charge more on that lane to incentivize people to use the other lanes instead. If all lanes are flowing equally, they will be priced (mostly) equally. In this case, the slowness was based on weather conditions and plow trucks not because all the traffic was on express lane and all other lanes were empty. Clearly, their algorithm needs to take road conditions into account when creating this prices. I didn't read this as a premium to use the express lane or only allow rich people to get home, just an unintended consequence of a beneficial program finding an edge case.
- mikeash 10y ago
  There aren't separate charges for separate lanes. There's a set of express lanes, which get a dynamic per-mile charge based on conditions, and a set of normal freeway lanes which cost nothing. The intent is to set the express lane pricing to a level that keeps their speed at 45MPH or more. The free lanes just do whatever.

by j1vms 10y ago

pavel_lishin 10y ago

So the problem here is more of a faulty algorithm?

denzil_correa 10y ago
You wouldn't know, you'd have to audit the algorithm to reveal the details.
Vivtek 10y ago
Less a "faulty algorithm" and more a moral hazard. The intent of the rules is to limit usage during periods of congestion not caused by the road operators themselves. The distinction is that human actors are not moral-free mechanisms.
- deleted 10y ago
  [deleted]

totally 10y ago

Right, traffic density increased without a corresponding increase in throughput.

6DM 10y ago

Honestly, I only saw a few flurries. I think everyone saw that and hopped on the express lanes. The day before a little rain fell and there were accidents everywhere. Guessing it was fresh on our collective minds. I passed a lot of cars in the express lanes on my way home. Cringing at the though of what car accidents lay ahead, but everything was clear.

aninhumer 10y ago

Arguably though, if the capacity of the road is reduced, then charging more for what remains is supply and demand, right?

denzil_correa 10y ago
In that case, one could charge $100 right? The capacity of the road is reduced then as well.
- aninhumer 10y ago
  No, I'm not saying the price increase is reducing capacity. I'm saying the trucks are reducing capacity (i.e. supply) and so the price is rising in response.
  - denzil_correa 10y ago
    > I'm saying the trucks are reducing capacity (i.e. supply) Source?
    - aninhumer 10y ago
      The comment I was originally replying to? >> the company (said) two salt and plow trucks were working on the southbound Express Lanes on I-495 and I-95, causing traffic to slow
      - denzil_correa 10y ago
        Now, I go back to my original question : Why is $30 the price that will do so? It could be $5 or $100.
        aninhumer 10y ago
        Well I don't know exactly how their algorithm works, but I'd guess they keep track of average travel times by scanning licence plates, and then raise prices when they go below the target speed, and lower them again when speeds increase?

claydiffrient 10y ago

I think perhaps it worked as intended right? The goal seems to be to keep traffic free flowing in the lane. > Tolls for the Express Lanes are dynamic, meaning they change periodically based on real-time traffic conditions to keep the Lanes free-flowing. > However, rates may rise significantly above the typical range for periods of time in the event of unusually heavy congestion or a specific event like a traffic accident or lane(s) closure. So because the trucks were slowing things down the price raised deterring more vehicles from entering and slowing this down more. It makes sense to me. ¯\_(ツ)_/¯

snarf21 10y ago

Maybe I misread this but my understanding is that the algorithm is intended to have all lanes have the same flow rate. If one lane is slow, charge more on that lane to incentivize people to use the other lanes instead. If all lanes are flowing equally, they will be priced (mostly) equally. In this case, the slowness was based on weather conditions and plow trucks not because all the traffic was on express lane and all other lanes were empty. Clearly, their algorithm needs to take road conditions into account when creating this prices. I didn't read this as a premium to use the express lane or only allow rich people to get home, just an unintended consequence of a beneficial program finding an edge case.

mikeash 10y ago
There aren't separate charges for separate lanes. There's a set of express lanes, which get a dynamic per-mile charge based on conditions, and a set of normal freeway lanes which cost nothing. The intent is to set the express lane pricing to a level that keeps their speed at 45MPH or more. The free lanes just do whatever.