Transit Can Cut Car Traffic Much More Than Ridership Alone Suggests

Portland's Max Blue Line Light Rail helped reduce driving far more than its ridership numbers would suggest, a new study finds. Photo: TriNet
Portland’s MAX Blue light rail line helped reduce driving far more than you would expect based on ridership alone. Photo: TriMet

How much traffic does a transit line keep off the streets? Looking at ridership alone only tells part of the story, according a new study published in the Journal of the American Planning Association. The full impact of a transit line on motor vehicle traffic can far exceed the direct effect of substituting rail or bus trips for car trips.

Using data from the Portland region, University of Utah researchers Reid Ewing and Shima Hamidi compared self-reported travel in an area where a light rail line was built to an area that saw no transit investment.

The team collected data on changes in travel behavior in the area served by the MAX Blue light rail line and in the area around SW Pacific Highway. They compared stats from 1994 — before light rail was built — and 2011 — 13 years after it launched. They opted to use the 2011 data in order to show the full impact of denser, transit-oriented development around the stations.

Ewing and Hamidi found that light rail led to an average of 0.6 additional transit trips per day among each household in the surrounding community. By itself that would have cut total driving mileage by about a half mile per household per day — not a huge impact.

But the effect on driving among households living near light rail was much greater than that.

From 1994 to 2011, households in the area without new transit increased their driving by 62 percent (from 18.25 miles per day to 29.4), while households living near the new light rail line increased their driving only 22 percent (from 17.4 miles to 21.2).

Why was this effect so much larger than the effect directly attributable to new transit trips? Partly because households living near the light rail walked more and traveled shorter distances when they did drive. Walking increased 151 percent among people living in the transit-oriented communities, Ewing and Hamidi found.

That was possible because, following the addition of light rail, city, regional, and state agencies took steps to encourage walkable development around the transit line. And it worked. According to Ewing and Hamidi the “activity density” of the light-rail neighborhoods — a measure of how many households and jobs are located in a given area — rose 100 percent between 1994 and 2011.

The total driving mileage avoided by households living near transit amounted to three times the avoided mileage due solely to switching from driving to transit. Similar studies have estimated this “multiplier effect” to be in the range between 1.9 and 9.

52 thoughts on Transit Can Cut Car Traffic Much More Than Ridership Alone Suggests

  1. Well obviously if there is some sort of transit line (could be anything not necessarily light rail) a certain % will use it. That’s just common sense

  2. One of the important observations is this:

    ” . . . following the addition of light rail, city, regional, and state agencies took steps to encourage walkable development around the transit line.”

    Major capital project evaluation and investment decision-making both feature — as a deeply rooted bias — the core assumption that people that have always driven will continue to drive no matter what the investment we make, be it transit or incremental road capacity. Mode shift just doesn’t happen, the models predict.

    Furthermore, and this is why the observation is particularly relevant:

    In today’s major capital project evaluation and investment decision-making processes, the absence of existing transit-supportive land-uses is used as an explanation as to why transit wouldn’t work, even if we were to make the investment. Here, however, we have yet another example of where the transit-and walking-supportive development came after the line – an investment enabled the land-use changes that in-turn increase transit ridership while at the same time reducing VMT for non-transit riders.

    Indeed, it is not the chicken or the egg argument it has been made out to be: It is , more simply, just a question of making better investments that support the outcomes we are seeking to achieve.

    The metrics and modeling assumptions we currently rely upon fail to account for changes in behavior that can be influenced by our investment decisions – such influence is severely understated due, in part, to failure to account for the synergistic effects that extend beyond the meager ridership increases many models predict.

    We need to begin making more transit investments to not only increase transit ridership, but to leverage significant benefits not presently recognized or considered during alternatives evaluation. Unless and until we do, our plans may set auspicious goals supporting a robust vision, but that vision is illusory – shadows on the wall of a cave.

  3. Angie- it is not “Portland’s” light rail. Check a fact, will ya? How would you like it if I conflated Cleveland, Columbus & Philadelphia?

    It is nice that the Max Line runs near Intel. And, suburban Beaverton and suburban Hillsboro (served by TriMet’s light rail) have done a good job attracting and retaining high tech. But light rail and TOD have been a bust in other areas- for instance in the planning disaster known as East Portland (a epic New Urbanist fail). We have new Orange line that stops in the middle of no where. Given where we are in the business cycle, and the impending real estate bust- the new Orange Line is likely to disappoint.

  4. It’s not “transit investment” – it’s developer subsidies. The developments along our light rail and streetcar lines are taxpayer-subsidized.

  5. Better to “subsidize” transit and compact development than to continue the decades-old practice of subsidizing decentralization and road building, much to our collective harm.

    Subsidy as community investment versus subsidy as community harm.

    “Subsidy” is among the most misunderstood terms that people throw around like molitiv cocktails in an incendiary effort to drag public investments through the mud.

    The conversation needs to be focused on outcomes – what did the investment yield, and was it worth it, direct and indirect benefits accounted for?

    Simple association with a bad word is child’s play. We’re adults here.

  6. Angie- it is not “Portland’s” light rail. Check a fact, will ya?

    Okay, will do.

    That sure looks like Portland to me. Given that the system operates entirely in Portland and nearby suburbs, I’m really not sure what the point of your analogy to Columbus and Philadelphia (two cities that are hundreds of miles apart) is.

  7. Hillsboro is not a suburb of Portland. They are miles apart culturally and have different leadership. They are in different counties. I say that City Lab’s mis-understanding of Oregon’s history and geography is just an attempt to amplify the false impression of Portland as a New Urbanist utopia.

    So yeah- it’s like confusing Cleveland and Columbus. Maybe now you know how we feel when you confuse downtown Portland with east Portland or Hillsboro.

  8. Political boundaries matter. So what if the census bureau didn’t say Vancouver-Portland- Beaverton. City Lab should stick to things it knows and not put false impressions out there. Hillsboro is a free-standing city miles from Portland with its own history and culture. The high tech companies deliberately avoided Portland for a reason. Your anti-rural bias is showing.

    Portland’s narcissism is a regional joke. The city is deeply divided and somewhat disfunctional.

  9. I have, no less than a month ago in fact. It all looks like the same smear of suburb to me. The center of Hillboro is closer to the center of Portland than several Chicago neighborhoods are to the Loop. Hillsboro is included in the Portland Urban Growth Boundary. A random political boundary might run through the middle of the neighborhoods, but it’s still a suburb.

  10. I’ve looked pretty closely, and I’ve talked to people. Face it. You’re a suburb of a city you hate.

  11. Look up “Beaverton Round”. Subsidized with millions in tax dollars, it nonetheless went bankrupt. Twice. And then there was the water damage. If you believe that you’re an adult, why not act like one? Adults aim for some degree of fiscal responsibility; children (like ravens) are attracted to shiny objects.

  12. Hillsboro is a free-standing city miles from Portland

    “Miles”? Less than 20 miles. Not very far, and well within the normal limits of what is considered a “suburb” of a large city.

    Your anti-rural bias is showing.

    Observing that cities have suburbs is “anti-rural bias”? How does that work, exactly?

    (Also, my city is a lot more rural than yours, and has less than half the population. I also don’t live in a suburb of one of the most populous cities in the country.)

    Hillsboro is a free-standing city miles from Portland with its own history and culture

    And Royal Oak and the Grosse Pointes are distinct from the city of Detroit… but that doesn’t change the fact that they are suburbs.

  13. Oh, balderdash from someone who doesn’t know the area. It’s a cottage industry, I suppose.

  14. Oh shut up, PN. I am sucessful at lobbying and I love Portland- the real Portland. Sorry that your New Urbanist bs is being rejected by your fellow Portlanders.

    Patking minimums anyone? Oh yeah! We got them back. Demolitions of small houses for McMansions- progress made there.. Busses instead of light rail on Powell- check. I am coming out ahead. Call me names, but you are not my audience.

    Right now, some reasonable fact-based folks are being turned onto the fact that CityLab isn’t big on fact-checking.

  15. Sorry that your New Urbanist bs is being rejected by your fellow Portlanders.

    So now you’re flip-flopping and claiming to be a Portlander, instead of a resident of a city that is “miles apart culturally”?

    Right now, some reasonable fact-based folks are being turned onto the fact that CityLab isn’t big on fact-checking.

    Are you so busy commenting that you forgot what website you’re on?

  16. Welcome, dear Streetsblog author, to the venerable west-coast tradition of Being Entitled To Your Own Facts.

    It’s actually a bit of a shame that the conversation has been diverted this way, because beneath all of Mamacita’s lunacy is an actual, valid point: Portland really isn’t the functional Transitopia that the national media so often shorthand it as. There have been any number of egregious planning mistakes that have palpably harmed or neglected mobility within the city proper’s mid-density areas (whose residents vastly outnumber those of showpieces like The Pearl, or of failed “TOD” placemaking like the South Waterfront).

    Portland also has ongoing, serious employment and economic-inequity troubles. It is worth being credulous of studies that paint an overly rosy picture of Portland outcomes, but for reasons (mostly) unrelated to Mamacita’s weird hair-splitting and false equivalencies.

  17. Where/when did I say I lived in Hillsboro? I am a long-time Portland resident (Eastside) and I have friends in Hillsboro, Helvetia and the environs. I also know my state.

  18. In PDX, we do it through tax breaks and waiving charges and indirectly through an unfair property tax arrangements whereby a 300,000 house close-in pays 50% of the tax paid by a house in Outer SE. The crappier your neighborhood- the higher the taxes. And, the Mayor spends $ downtown and close-in neighborhoods. That’s what you see in pictures.

    Max on the Eastside is ugly, with no TOD- just weeds and transients and the occasional mall.

  19. I love the word “ornery.” Up vote! My part of Portland is kinda down home rural and I like it.

  20. DP,

    I actually hate the subject of urban/transit planning and only blog because my city let me down. I don’t know what the right way is to plan for growth- but I see what is exactly the wrong thing to do and that is what Portland is preparing to do.. If Portland had a good Mayor I would never visit CityLab again.

    Step up, for god sakes. The shallow dogmatic group-thinkers like Alicia would cause anyone to howl at the moon. Over and out, and for god sakes point out the factual errors so I don’t have to.

  21. How do you define the “suburb” relationship? People work in PDX and live in Hillsboro, and (this is important)
    work in Hillsboro and live in PDX. This idea that Hillsboro is a “bedroom” suburb of Portland and somehow controlled by Portland is not true. I guess my objection is that Port;land takes credit for things that happen in other
    cities (Vancouver) and other counties (Washington, Clackamas).

    The money & power is in Washington County- not PDX. So I guess I reject the relationship that “Suburb of” implies in this case. PDX gets no credit for Washington County’s success. Hillsboro is not in Portland’s shadow. That is not Portland’s Max. It’s Tri-Met.

  22. Developments around freeways and arterials are not subsidized, Jym. Try again.

    And do some research next time. It helps if you know what you’re trying to talk about.

  23. If Portland had a good Mayor I would never visit CityLab again.

    So you’re hung up with nitpicking Streetblog for saying “Portland” instead of “TriMet”, but you have no problem with referring to Streetsblog as Citylab? Talk about factual errors.

  24. Boy, I don’t really get what that was about, but we described it the way the study authors described it. I don’t claim any special knowledge about Portland.

  25. There is a flase narrative about “Portland,” and I am sick of it. Why don’t you contact me off line and I will clarify what is really going on in this area.

  26. It’s entirely suburban. Those that live the “rural” weekend play-farmer or full-time farmer lifestyle are a tiny fraction of the total population now. I know, I have friends and in-laws that live out there.

  27. That is an interesting article and I will read it. I am open to changing my theory based on facts. But before you get so rude, remember that for years the data pointed towards stronger growth in Washington County. This may be a lasting or temporary change in the trend. It should be noted that Boeing Gresham,, Nike and Intel etc have big capital investments and are less likely to move than the satelittle offices of software comapnaies opeing up in Portland.

    I am open to facts. Let’s see if the trend lasts. Where do you think we are in the economic cycle?

    Hopefully Portland won’t crater when real estate and high tech go through their periodic downturns. Intel will lay people off- but not pull up stakes. AirBnB etc- they can move easily if something changes. That’s my concern for Portland- that it is a house of cards.

  28. By “Max on the Eastside”, which line(s) are you referring to? I’d like to compare them against Google street view or other photographs to see if I can get an idea of how they look.

  29. @MaxRedline – Research, you say? Some citations would be helpful to dispel my supposed ignorance. I shall await them with bated breath.

  30. Texas makes the developer build the roads, the sewage, the water, the electrical, then incorporate into a municipal utility district.

    Pennsylvania, Cranberry Township requires the developer to pay for all improvements (including increased traffic) prior to approving plans.

    Lazy Lefty, aren’t you Jym? The mating call of the lazy Lefty with no argument is: “citation needed”.

  31. @MaxRedline – Cranberry benefits from the infrastructure in adjacent Allegheny County, originally U.S. Rt. 19 and more recently, Interstate I79, plus the I279 spur that brings its retail customers up from Pittsburgh. These were of course built with piles of taxpayer money, not to mention the properties taken away by eminent domain. Cranberry has an I79 offramp to Walmart that was built at public expense following a typical Walmart threat to move somewhere else. The recent work on State Route 228 in Cranberry was paid for with state revenues, not by developers.

  32. High winds and severe storms ripped through the area.

    – June, 2014.

    That explains the “recent work on SR 228”. Anything else?

  33. Hi, PN: you may be unaware of this, but crime associated with the MAX line to Gresham got so bad that the mayor there devoted city police resources to patrol the area along the line. In Rockwood, we used to have a Fred Meyer center (with a dozen or so ancillary stores). All of those shut down within a few years of the light rail line going live. They cited increased thefts and assaults. A few years later, the Safeway closed, citing identical reasons.

  34. @MaxRedline – According to the PennDOT website the project started in Fall 2012, which suggests some amazing prescience about those June 2014 storms.

  35. Oh, yes. Since you stated “recent”, I assumed you meant “recent”, when you meant “two years ago”. Nonetheless, they require the developer to pay for all improvements. Generally, when the improved road is turned over to the city or state, maintenance falls to that receiving entity.

    Here, for example, Walmart has built a new store, and they’re paying for road improvements including signalization. It’s pretty common. The development itself is not subsidized, which I believe was the point behind my original comment.

    By contrast, light rail and streetcar lines are entirely subsidized, as are the developments that they supposedly “spur”.

  36. I guess since the round in Beaverton went bad, we should all give up on govt-subsidized TODs and revert to good ol fashioned sprawl. Until all the flat land in the country is one big suburb, except for New York and Chicago and places like that I dunno. But hey walmart and Safeway paid for the roads.

  37. I’m curious why researchers from Salt Lake City would look at Portland rather than Salt Lake City, which also has light rail lines and TOD?

    Salt Lake’s light rail system is pretty fantastic, btw.

  38. This study was actually conducted as part of the larger research effort of TCRP Project H-46 (forthcoming), which collected data in various ways from around the country in order to measure the impact of transit on land use patterns and subsequently VMT and GHG at the regional/system, corridor and station area scales. The longitudinal data from Portland was well structured to conduct this type of analysis at a corridor level, so the research team used this as a case study. (I am aware of this because I served on the project panel). The same analysis could be conducted in other regions if the same set of longitudinal data were available.

    Reid Ewing has also recently published an interesting study of the reduction in car travel volumes in one of the TRAX corridors (University Line) in Salt Lake, so he does work closer to home as well:

    I encourage Streetsblog readers interested in the topic to seek out these studies and read them directly.

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