Google Maps Experiment Shows How Small Routing Changes Reduce City Traffic
The power of collaboration: How we can reduce traffic congestion
We conducted a large-scale experiment across ten major US cities to test if coordinating a tiny fraction of trips could ease congestion. By subtly guiding drivers away from bottlenecks using Google Maps, we achieved measurable speed increases and fuel savings city-wide. This study proves that even minor, system-wide routing adjustments can significantly improve traffic flow and reduce emissions for everyone, not just app users.
By coordinating a small fraction of trips, we can achieve systemic gains that benefit all road users — not just those using a specific app.
- wxw
> For this study, the Google Maps algorithm was modified to prefer alternative routes with similar travel times and segment types, effectively guiding trips away from the pre-selected congested segments
> Over a six month period, we adopted a city-wide switchback (also known as crossover) experimental design, alternating between this treatment and the control (unaltered) routing algorithm over consecutive days to appropriately measure the effect of this intervention
> Averaged across cities, we observe a median increase of around 2% in driving speeds on targeted segments, corresponding to a median decrease of 0.5% to 1.0% in fuel consumption rates
The cities were: Atlanta, Boston, Chicago, Los Angeles, Miami, New York, Philadelphia, Salt Lake City, San Francisco, Seattle.
The data and code is also available (https://github.com/google-research/google-research/blob/mast...) from the paper (https://www.nature.com/articles/s44284-026-00443-x).
Kudos Google! Nice to see this kind of work. That said, let's just build more trains?
- trymas
How we can reduce traffic congestion?
1. Extensive support of public transport: metro, tram, dedicated bus routes (separate from car traffic), dedicated paths for bicycles.
2. ... maybe whatever is this ...
UPDATE: here's a good graph - https://en.wikipedia.org/wiki/Public_transport#/media/File:P... , i.e. car traffic is often congested because of inherent low passenger bandwith. If google wants to manage traffic as internet routing - why then stick with outdated low bandwith ethernet cable?
- jawns
One of the things this type of intervention doesn't take into account is that different roads are built with different levels of hardiness based on the amount of traffic they are expected to receive.
For instance, a few years ago, a segment of I-495 in Delaware needed to be unexpectedly shut down for emergency repairs. Drivers were rerouted. But because of the increase in traffic on the less-hardy detour route, that route needed repairs and repaving soon afterward, much more quickly than it would have ordinarily required.
So yes, drivers can be better dispersed to ease congestion, but we also need to consider the secondary effects to the roadways themselves.
- ctkhn
Surely the top way to avoid traffic congestion would be communities where it's possible to live near where you work, shop, go out, etc. and not doing everything else exactly the same but taking a slightly different highway in your car
- ventana
The same things keeps happening every time I find myself stuck in traffic on the interstate. Out of nowhere, a popup appears in Google Maps: a faster route is available! 4 minutes faster! Unless either the passenger or the driver are fast enough to hit "No thanks", the change auto-applies, and Google now wants me to exit the interstate at the nearest exit and drive some random road I had no idea about, to rejoin the interstate a few miles ahead. Of course, a bunch of other vehicles in the same traffic jam got the same
notification, so that minor road now get a sizable fraction of the interstate traffic, all of which then struggles to merge back.
Seeing this again and again. We call it a "Google detour" in the family, and rarely agree to the change of the route.
- zip1234
Congestion can be solved by charging more for driving. Even a modest amount would start affecting how much people drive. The money could be used for better roads and improving other transit options that aren't so space-inefficient. That said, this would likely be unpopular to implement until the effects were visible. See congestion pricing in NYC as an example.
- nostrademons
I've noticed that Google Maps has started sucking a lot lately, routing us onto routes that take 2-4 minutes longer when a faster route is clearly available or taking us on nonsensical detours, and I wonder if this experiment is a reason why.
There's a hidden cost to this, and that's trust in the mapping app. I've stopped using Google Navigation for routine trips where I know how to get to the destination. It used to be worth it for the traffic information, but now that there's a good chance that it'll take you on a slower route for reasons that may be beneficial to Google but detrimental to you, it's not worth it. My brother-in-law switched to Apple Maps for similar reasons: he's finding it simply gives better results nowadays.
- dtgriscom
Traffic apps only know about congestion if someone running the app goes down the congested road. Because of this, I've always suspected that the apps, from time to time, will route someone down a route they haven't gathered data on in a while, just to collect the data, and even if the route is likely to be suboptimal.
- pretzellogician
"Hence, the efficient use of transportation networks is of paramount importance."
Perhaps some sort of carpooling profile? That would be a dramatically bigger improvement than, say, routing users through residential neighborhoods.
- mwexler
I'm a fan of Beaty's work from 1998. Nothing I've seen has been as easy to implement: leaving space in front of each car creates smooth motion.
https://trafficwaves.org/trafexp.html or easier at https://web.archive.org/web/20260114173129/https://trafficwa...
https://web.archive.org/web/20251214172912/http://trafficwav... has some nice visualizations.
MIT got more press when they "rediscovered" this in 2017:
https://people.csail.mit.edu/bkph/Traffic_Flow_Animation
I'm a car fan, so I'd rather reward drivers for optimal behaviors vs broad car-reductions. I'll probably turn out to be on the wrong side, but maybe we'll find a good compromise.