5 ms·
This isn't what they studied, but a simple thought experiment shows a limited use case where traffic absolutely can be helped by speeding things up. Let's imag
by mjevans 7y ago
This isn't what they studied, but a simple thought experiment shows a limited use case where traffic absolutely can be helped by speeding things up.
Let's imagine a world where self driving cars are required for freeway driving; this allows them to respond in a predictable and timely manor with respect to directives to avoid lanes (and not jump the line) as well as to go at an exact speed.
An event (accident, whatever) obstructs One of Five possible lanes for use (including the HOV lane) on a section normally rated at 60 MPH.
This reduces the capacity of the road by 1/5th, or alternately, one lane of flow should be re-distributed across 4 lanes (1/4th per lane).
Idealized solution: A temporary bypass zone is communicated to the self-driving cars. There is a lead up zone where the speed is expected to ramp up to the new target, followed by a merge zone where the lanes reduce and the flow is re-shaped to balance traffic evenly. The cars would then pass the incident zone in this higher speed lane-compressed flow, before expanding out and then slowing back down to normal speed.
Due to the unexpected nature of the incident there has also been a buildup of volume before the incident, so to alleviate that slightly higher flow will be allowed to drain the high pressure area.
In the above hypothetical case, for 4 out of 5 lanes nornally at 60MPH, I would prefer to imagine: (1 + 1/4) * 60MPH => 75, but round up another 5 MPH for the bypass flow for a total of 80MPH in the corrected flow area.
Many sections of freeway could likely support that safely ; they're often engineered very well but have conservative speed limits set for political and driver quality reasons. However some sections would 'cap out' at a lower actually safe speed; in those sections the above procedure could help minimize the traffic flow impact.
However... CGP Grey really nailed the real problem: https://www.youtube.com/watch?v=iHzzSao6ypE https://www.youtube.com/watch?v=iHzzSao6ypE
- dev_dull 7y ago> Idealized solution: A temporary bypass zone is communicated to the self-driving cars. There’s so many great opportunities like this once the cars are self driving and connected. For example, a ten lane highway without dividers! 8v2 split depending on the time of day and traffic patterns. How many times have you been stuck in a lane with the other lanes in the other direction completely open?
- fuzz4lyfe 7y agoYou could open up lanes a quarter mile at a time even depending on traffic demands. Eg. Between exit 1 and exit 2, 8 northbound lanes are open. Between 2 and 3 we have 6 northbound lanes. It's would be pretty disconcerting to travel in your self driving car and head full speed into oncoming traffic only to shift lanes a few moments before collision though.
- dsfyu404ed 7y agoThey had this in Montreal back in the day (i.e. the 1960s, when the risk of a head on crash was one you just accepted by driving). There would be a bunch of lanes undivided from each other and over the lanes would be lights telling you which lanes were open for your direction of travel. Movable barriers work too but are far more expensive.
- dev_dull 7y agoSeattle has this with a physically separated highway. It’s closed in one direction and switches directions around noon. Fun to wait at the entrance with a motorcycle. As soon as it’s open you have 5 miles where it’s physically impossible for another car to merge on.
- nostrademons 7y agoAlso, drafting. With human drivers it's not feasible to have cars travel 6 inches behind each other, because human reaction time is shitty enough that everybody would crash. With computer control you could easily have cars match speeds, then slowly get closer until they latch together and form a train. This'd both dramatically increase the carrying capacity of roads (with the default 1-car-length-per-10mph-of-speed rule, 7/8 of a highway is empty space), and it would improve fuel economy by reducing cross-sectional area and wind resistance.
- sushisource 7y agoThis is still a terrible idea. What happens when the car in front of you has an axel failure? Oops, my car's instant reaction time is worth nothing because the brakes cannot physically prevent my imminent death.
- deleted 7y ago[deleted]
- robocat 7y agoAlso introduce effective information to commuters to reduce flow: many drivers can vary their timing (come into work 2 hours later), or path (delivery schedule; go to a different office), or just cancel (go shopping tomorrow instead).