David Zipper
@davidzipper.bsky.social
Senior Fellow @ MIT Mobility Initiative & Contributing Writer @ Vox, focused on transport, cities and tech. Words in Atlantic, CityLab, WaPo, etc. https://linktr.ee/davidzipper
Newsletter, speaking and advisory work: http://davidzipper.com
Newsletter, speaking and advisory work: http://davidzipper.com
New research finds that ~18% of Americans would like to live car-free -- more than double the share that currently does.
doi.org/10.1016/j.tr...
doi.org/10.1016/j.tr...
February 11, 2026 at 1:37 PM
New research finds that ~18% of Americans would like to live car-free -- more than double the share that currently does.
doi.org/10.1016/j.tr...
doi.org/10.1016/j.tr...
I hear a lot about a future of "shared" AVs where riders travel with strangers. Not gonna happen.
Most people -- esp women, as per this study -- don't want to sit alone with someone stinky or creepy. Nor are they willing to let others' itineraries dictate their route.
doi.org/10.1016/j.tr...
Most people -- esp women, as per this study -- don't want to sit alone with someone stinky or creepy. Nor are they willing to let others' itineraries dictate their route.
doi.org/10.1016/j.tr...
February 10, 2026 at 1:28 PM
I hear a lot about a future of "shared" AVs where riders travel with strangers. Not gonna happen.
Most people -- esp women, as per this study -- don't want to sit alone with someone stinky or creepy. Nor are they willing to let others' itineraries dictate their route.
doi.org/10.1016/j.tr...
Most people -- esp women, as per this study -- don't want to sit alone with someone stinky or creepy. Nor are they willing to let others' itineraries dictate their route.
doi.org/10.1016/j.tr...
Very cool paper measuring pedestrian volumes on NYC streets and examining crash risks:
"Intersections with the highest pedestrian injury risk are often outside Manhattan, where exposure-adjusted danger is the greatest."
www.nature.com/articles/s44...
"Intersections with the highest pedestrian injury risk are often outside Manhattan, where exposure-adjusted danger is the greatest."
www.nature.com/articles/s44...
February 9, 2026 at 4:35 PM
Very cool paper measuring pedestrian volumes on NYC streets and examining crash risks:
"Intersections with the highest pedestrian injury risk are often outside Manhattan, where exposure-adjusted danger is the greatest."
www.nature.com/articles/s44...
"Intersections with the highest pedestrian injury risk are often outside Manhattan, where exposure-adjusted danger is the greatest."
www.nature.com/articles/s44...
US bike safety has been an absolute disaster over the last 15 years.
2024 saw the highest number of deaths on record.
bikeleague.org/another-year...
2024 saw the highest number of deaths on record.
bikeleague.org/another-year...
February 8, 2026 at 3:28 PM
US bike safety has been an absolute disaster over the last 15 years.
2024 saw the highest number of deaths on record.
bikeleague.org/another-year...
2024 saw the highest number of deaths on record.
bikeleague.org/another-year...
New paper finds that US bike deaths have "trended toward lower-density suburban areas" rather than central cities
Those killed tend to be poor and non-white.
Lesson: The suburbanization of poverty could be contributing to the surging number of cyclist fatalities.
doi.org/10.1016/j.jc...
Those killed tend to be poor and non-white.
Lesson: The suburbanization of poverty could be contributing to the surging number of cyclist fatalities.
doi.org/10.1016/j.jc...
February 8, 2026 at 3:26 PM
New paper finds that US bike deaths have "trended toward lower-density suburban areas" rather than central cities
Those killed tend to be poor and non-white.
Lesson: The suburbanization of poverty could be contributing to the surging number of cyclist fatalities.
doi.org/10.1016/j.jc...
Those killed tend to be poor and non-white.
Lesson: The suburbanization of poverty could be contributing to the surging number of cyclist fatalities.
doi.org/10.1016/j.jc...
Biking is also great for the middle aged.
This new study found a "positive association between cycling and cognition in adults ≥45 years of age."
doi.org/10.1016/j.jc...
This new study found a "positive association between cycling and cognition in adults ≥45 years of age."
doi.org/10.1016/j.jc...
February 6, 2026 at 1:56 PM
Biking is also great for the middle aged.
This new study found a "positive association between cycling and cognition in adults ≥45 years of age."
doi.org/10.1016/j.jc...
This new study found a "positive association between cycling and cognition in adults ≥45 years of age."
doi.org/10.1016/j.jc...
I'll soon head to the Sunshine State to keynote the Safe Roads Summit in Fort Lauderdale.
My topic: How cities can prepare for an influx of AVs.
I'll be joined by @wesmars.bsky.social, my partner in crime on @lookbothwayspod.bsky.social.
Info: www.browardmpo.org/safe-roads-s...
My topic: How cities can prepare for an influx of AVs.
I'll be joined by @wesmars.bsky.social, my partner in crime on @lookbothwayspod.bsky.social.
Info: www.browardmpo.org/safe-roads-s...
February 5, 2026 at 1:47 PM
I'll soon head to the Sunshine State to keynote the Safe Roads Summit in Fort Lauderdale.
My topic: How cities can prepare for an influx of AVs.
I'll be joined by @wesmars.bsky.social, my partner in crime on @lookbothwayspod.bsky.social.
Info: www.browardmpo.org/safe-roads-s...
My topic: How cities can prepare for an influx of AVs.
I'll be joined by @wesmars.bsky.social, my partner in crime on @lookbothwayspod.bsky.social.
Info: www.browardmpo.org/safe-roads-s...
"The annual traffic fatality rate per 100k people increased by more than 33% across the 100 largest US cities but less than 5% in all other parts of the country [between 2008-12 and 2018-22]."
findingspress.org/article/1559...
findingspress.org/article/1559...
February 4, 2026 at 9:36 PM
"The annual traffic fatality rate per 100k people increased by more than 33% across the 100 largest US cities but less than 5% in all other parts of the country [between 2008-12 and 2018-22]."
findingspress.org/article/1559...
findingspress.org/article/1559...
Recommended reading for anyone trying to wrap their head around today’s WaPo news
www.linkedin.com/posts/mabaro...
www.linkedin.com/posts/mabaro...
February 4, 2026 at 6:16 PM
Recommended reading for anyone trying to wrap their head around today’s WaPo news
www.linkedin.com/posts/mabaro...
www.linkedin.com/posts/mabaro...
New research finds negligible benefit from "minimum passing distance" laws requiring drivers to give cyclists space when overtaking them.
Protected bike lanes are far more effective.
doi.org/10.1016/j.jc...
Protected bike lanes are far more effective.
doi.org/10.1016/j.jc...
February 3, 2026 at 1:23 PM
New research finds negligible benefit from "minimum passing distance" laws requiring drivers to give cyclists space when overtaking them.
Protected bike lanes are far more effective.
doi.org/10.1016/j.jc...
Protected bike lanes are far more effective.
doi.org/10.1016/j.jc...
Ridehail worsens many urban problems (esp congestion), but it does reduce traffic fatalities.
This new paper found that ridehail lowers crash deaths by 5.2%, with decreases concentrated after dark when people are more likely to drink.
doi.org/10.1162/rest...
This new paper found that ridehail lowers crash deaths by 5.2%, with decreases concentrated after dark when people are more likely to drink.
doi.org/10.1162/rest...
February 2, 2026 at 6:16 PM
Ridehail worsens many urban problems (esp congestion), but it does reduce traffic fatalities.
This new paper found that ridehail lowers crash deaths by 5.2%, with decreases concentrated after dark when people are more likely to drink.
doi.org/10.1162/rest...
This new paper found that ridehail lowers crash deaths by 5.2%, with decreases concentrated after dark when people are more likely to drink.
doi.org/10.1162/rest...
But to date, Waymo, Tesla, Zoox, et al. have ignored rural areas in favor of cities.
In their defense, rural deployments are hard:
- Longer trips ➡️ Lower robotaxi utilization
- Fewer lane markers and curbs
- Spotty cell service
- Different vehicles like Amish buggies, harvesters, etc
In their defense, rural deployments are hard:
- Longer trips ➡️ Lower robotaxi utilization
- Fewer lane markers and curbs
- Spotty cell service
- Different vehicles like Amish buggies, harvesters, etc
February 2, 2026 at 3:01 PM
But to date, Waymo, Tesla, Zoox, et al. have ignored rural areas in favor of cities.
In their defense, rural deployments are hard:
- Longer trips ➡️ Lower robotaxi utilization
- Fewer lane markers and curbs
- Spotty cell service
- Different vehicles like Amish buggies, harvesters, etc
In their defense, rural deployments are hard:
- Longer trips ➡️ Lower robotaxi utilization
- Fewer lane markers and curbs
- Spotty cell service
- Different vehicles like Amish buggies, harvesters, etc
If AVs were widely available, they could dramatically improve rural mobility and enhance safety.
Better yet, as they scale they pose little risk of causing congestion or sprawl, or of undermining transit. (Unlike cities, the countryside is already built around the automobile.)
Better yet, as they scale they pose little risk of causing congestion or sprawl, or of undermining transit. (Unlike cities, the countryside is already built around the automobile.)
February 2, 2026 at 3:00 PM
If AVs were widely available, they could dramatically improve rural mobility and enhance safety.
Better yet, as they scale they pose little risk of causing congestion or sprawl, or of undermining transit. (Unlike cities, the countryside is already built around the automobile.)
Better yet, as they scale they pose little risk of causing congestion or sprawl, or of undermining transit. (Unlike cities, the countryside is already built around the automobile.)
Rural transportation has deep challenges:
🔹 High crash death rates
🔹 Long drives mean private cars are often the only way to travel (minimal transit/taxis/ridehail)
🔹 Car ownership is expensive due to high mileage, maintenance, and a shortage of mechanics
🔹 Many forgone trips to work, a doctor, etc
🔹 High crash death rates
🔹 Long drives mean private cars are often the only way to travel (minimal transit/taxis/ridehail)
🔹 Car ownership is expensive due to high mileage, maintenance, and a shortage of mechanics
🔹 Many forgone trips to work, a doctor, etc
February 2, 2026 at 2:59 PM
Rural transportation has deep challenges:
🔹 High crash death rates
🔹 Long drives mean private cars are often the only way to travel (minimal transit/taxis/ridehail)
🔹 Car ownership is expensive due to high mileage, maintenance, and a shortage of mechanics
🔹 Many forgone trips to work, a doctor, etc
🔹 High crash death rates
🔹 Long drives mean private cars are often the only way to travel (minimal transit/taxis/ridehail)
🔹 Car ownership is expensive due to high mileage, maintenance, and a shortage of mechanics
🔹 Many forgone trips to work, a doctor, etc
Research shows that biking is very, very healthy for people 65+.
Findings after reviewing 28 prior studies:
"Cycling in later life links to improved mobility [and] balance."
"Older cyclists often report psychosocial health, life satisfaction, and well-being improvements."
doi.org/10.1016/j.jt...
Findings after reviewing 28 prior studies:
"Cycling in later life links to improved mobility [and] balance."
"Older cyclists often report psychosocial health, life satisfaction, and well-being improvements."
doi.org/10.1016/j.jt...
February 1, 2026 at 3:44 PM
Research shows that biking is very, very healthy for people 65+.
Findings after reviewing 28 prior studies:
"Cycling in later life links to improved mobility [and] balance."
"Older cyclists often report psychosocial health, life satisfaction, and well-being improvements."
doi.org/10.1016/j.jt...
Findings after reviewing 28 prior studies:
"Cycling in later life links to improved mobility [and] balance."
"Older cyclists often report psychosocial health, life satisfaction, and well-being improvements."
doi.org/10.1016/j.jt...
New research finds that the vast majority of US pickup owners would be just fine going electric.
3 in 4 either prefer an EV or would be indifferent if performance and price are comparable.
doi.org/10.1016/j.tr...
3 in 4 either prefer an EV or would be indifferent if performance and price are comparable.
doi.org/10.1016/j.tr...
January 31, 2026 at 4:00 PM
New research finds that the vast majority of US pickup owners would be just fine going electric.
3 in 4 either prefer an EV or would be indifferent if performance and price are comparable.
doi.org/10.1016/j.tr...
3 in 4 either prefer an EV or would be indifferent if performance and price are comparable.
doi.org/10.1016/j.tr...
For all the hullabaloo over first-mil/last-mile solutions, 90%+ of US transit riders arrive at a station by means of their own two feet.
www.nationalacademies.org/projects/TRB...
www.nationalacademies.org/projects/TRB...
January 31, 2026 at 2:47 PM
For all the hullabaloo over first-mil/last-mile solutions, 90%+ of US transit riders arrive at a station by means of their own two feet.
www.nationalacademies.org/projects/TRB...
www.nationalacademies.org/projects/TRB...
Recent Danish paper suggests that transit's first-mile/last-mile discourse is overblown.
Pretty much any FM/LM "solution" fails to improve total welfare for distances <1km.
A big reason: Walking is really healthy!
link.springer.com/article/10.1...
Pretty much any FM/LM "solution" fails to improve total welfare for distances <1km.
A big reason: Walking is really healthy!
link.springer.com/article/10.1...
January 31, 2026 at 2:25 PM
Recent Danish paper suggests that transit's first-mile/last-mile discourse is overblown.
Pretty much any FM/LM "solution" fails to improve total welfare for distances <1km.
A big reason: Walking is really healthy!
link.springer.com/article/10.1...
Pretty much any FM/LM "solution" fails to improve total welfare for distances <1km.
A big reason: Walking is really healthy!
link.springer.com/article/10.1...
January 30, 2026 at 5:14 PM
The NBER researchers considered which other US cities might see comparable suburban speed benefits if they implement congestion pricing. Their criteria:
1) Powerful downtown
2) Congested suburbs
3) Many long commutes
Boston and Chicago both are both promising candidates.
1) Powerful downtown
2) Congested suburbs
3) Many long commutes
Boston and Chicago both are both promising candidates.
January 30, 2026 at 2:26 PM
The NBER researchers considered which other US cities might see comparable suburban speed benefits if they implement congestion pricing. Their criteria:
1) Powerful downtown
2) Congested suburbs
3) Many long commutes
Boston and Chicago both are both promising candidates.
1) Powerful downtown
2) Congested suburbs
3) Many long commutes
Boston and Chicago both are both promising candidates.
Residents of outer boroughs & suburbs – many of whom seldom drive into Manhattan -- have been among congestion pricing’s most vehement critics.
Their fears of surging traffic on "their" roads were unfounded. In fact, local traffic now flows faster.
www.northjersey.com/story/news/b...
Their fears of surging traffic on "their" roads were unfounded. In fact, local traffic now flows faster.
www.northjersey.com/story/news/b...
January 30, 2026 at 2:24 PM
Residents of outer boroughs & suburbs – many of whom seldom drive into Manhattan -- have been among congestion pricing’s most vehement critics.
Their fears of surging traffic on "their" roads were unfounded. In fact, local traffic now flows faster.
www.northjersey.com/story/news/b...
Their fears of surging traffic on "their" roads were unfounded. In fact, local traffic now flows faster.
www.northjersey.com/story/news/b...
As expected, drives into Manhattan grew notably faster following congestion pricing.
But local journeys outside the toll zone also sped up a bit – and there are *lots* of them.
To the researchers’ surprise, those driving outside Manhattan collectively saved 5x more hours than toll payers(!).
But local journeys outside the toll zone also sped up a bit – and there are *lots* of them.
To the researchers’ surprise, those driving outside Manhattan collectively saved 5x more hours than toll payers(!).
January 30, 2026 at 2:15 PM
As expected, drives into Manhattan grew notably faster following congestion pricing.
But local journeys outside the toll zone also sped up a bit – and there are *lots* of them.
To the researchers’ surprise, those driving outside Manhattan collectively saved 5x more hours than toll payers(!).
But local journeys outside the toll zone also sped up a bit – and there are *lots* of them.
To the researchers’ surprise, those driving outside Manhattan collectively saved 5x more hours than toll payers(!).
The finding comes from a new NBER study from researchers at Yale, Stanford, and Google.
Using anonymized Google Maps trip data, they measured how vehicle speeds changed following congestion pricing‘s implementation in NYC vis a vis peer cities in the US.
www.nber.org/papers/w33584
Using anonymized Google Maps trip data, they measured how vehicle speeds changed following congestion pricing‘s implementation in NYC vis a vis peer cities in the US.
www.nber.org/papers/w33584
January 30, 2026 at 2:12 PM
The finding comes from a new NBER study from researchers at Yale, Stanford, and Google.
Using anonymized Google Maps trip data, they measured how vehicle speeds changed following congestion pricing‘s implementation in NYC vis a vis peer cities in the US.
www.nber.org/papers/w33584
Using anonymized Google Maps trip data, they measured how vehicle speeds changed following congestion pricing‘s implementation in NYC vis a vis peer cities in the US.
www.nber.org/papers/w33584
This is the book (a lengthy and edited conversation btw Judt and his friend @timothysnyder.bsky.social).
And yes, it’s fascinating.
And yes, it’s fascinating.
January 30, 2026 at 12:51 AM
This is the book (a lengthy and edited conversation btw Judt and his friend @timothysnyder.bsky.social).
And yes, it’s fascinating.
And yes, it’s fascinating.
Curious to see what role car bloat may have played in the recent Waymo crash (with a child, near a Santa Monica elementary school)
January 29, 2026 at 7:47 PM
Curious to see what role car bloat may have played in the recent Waymo crash (with a child, near a Santa Monica elementary school)