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> Critics say that the road will simply attract more traffic, but the way in which it is managed means that traffic is dispersed and therefore means there is le

• throw0101a 4y ago
  > […] induced demand[0] mentioned; is there any truth in that? RAND Europe 2018 study for the UK Department for Transport, "Induced travel demand: an evidence review": > The objective of this study was therefore to review the empirical evidence on induced demand, with a view to understanding the size of the effect and where and under what conditions it occurs. In practice, measured induced traffic effects will depend on the time period over which they are measured, the geographical area and whether short-run or long run effects, particularly on land use, are included. While the impact of background growth is not included in this review, empirical studies of induced travel need to control for background traffic growth, as well as traffic changing route (reassigned traffic). […] > The evidence reviewed in this study supports the findings of the SACTRA (1994) report that induced traffic does exist, though its size and significance is likely to vary in different circumstances. It was not possible to obtain any qualitative understanding about the composition of induced traffic in terms of new trips, redistributed trips, transfers between modes and trips associated with new developments. There remain wide variations in the quantitative evidence that make it difficult to draw conclusions about the magnitude of the impact of induced demand from road capacity improvements on the Strategic Road Network. However, we draw some tentative conclusions: * https://www.gov.uk/government/publications/induced-travel-demand-an-evidence-review https://www.gov.uk/government/publications/induced-travel-de... * PDF: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/762976/latest-evidence-on-induced-travel-demand-an-evidence-review.pdf https://assets.publishing.service.gov.uk/government/uploads/... 2021 follow-up, "Induced travel demand: analytical research": * https://www.gov.uk/government/publications/induced-travel-demand-analytical-research https://www.gov.uk/government/publications/induced-travel-de... From the Netherlands: > The increase in traffic volume that arises after opening of new road infrastructure, is often attributed to ‘induced demand’. The objective of this study is to provide empirically derived insights in this phenomenon, in the amount of induced demand and in the benefits that adding road infrastructure has for users. Based on multivariate analyses of detailed data in The Netherlands from 2000-2012, it is concluded that the amount of induced demand in total is relatively low and that the relatively large increase in traffic volume during peak hours on roads that were congested before adding lanes mainly has been caused by shifts in route and departure time. The benefits of the new infrastructure for users have been calculated in terms of savings of travel time and travel time reliability. Implications for cost-benefit analyses of road investments have been reviewed. * https://doi.org/10.1016/j.trpro.2016.05.008 https://doi.org/10.1016/j.trpro.2016.05.008 Huge amounts of academic literature on this.
  • mgdlbp 4y ago
    Oh, I didn't read what I wrote! I meant to question the blog's argument that 'the way in which it is managed...means that traffic is dispersed'; I see how the 'that' binds to the closer noun now. Still, thanks for the refs on the topic in general--I never really researched it because its existence didn't seem contested. -- Re-reading the blog, I just realized that they're referring to the managed lane system described in the first paragraph. Looking it up now, it does not look very effective. The 2013 study of the results of its implementation by the Texas A&M Transportation Institute gives a good introduction: > The Katy Freeway Managed Lanes on I-10 in Houston became fully operational in 2009. The managed lane facility, also referred to as the Katy Tollway, is the first constructed managed lane project in Texas and the first variably priced operation in the state since the implementation of the QuickRide program on US 290 and I-10 HOV lanes in Houston more than 10 years ago. The four-lane facility, which was constructed within the center of the existing freeway, can be described as a "second-generation" managed lanes project that is more complex than earlier-generation HOV-to-HOT conversions. I gather that the added lanes (four in every source I could find, but six according to the blog?) were intended to relieve congestion during peak hours, and that the managed lane system was used instead of a simple widening indeed to limit induced demand, through both tolls and HOV restrictions (incentivizing carpooling). But: > Figure 4 shows that the daily traffic volumes on the managed lanes were fairly consistent from about 2001 through 2008, even during the construction period from 2004 through 2009. In 2009, after construction was complete, a dramatic increase in vehicle volume was observed, essentially doubling volumes over pre-expansion levels. They also note that "isolated sections of congestion have emerged on the GPLs [general-purpose lanes] despite the increase in general-purpose capacity provided by the freeway expansion" and that "off-peak volumes are growing at a rapid rate on the managed lanes". Still, they manage to arrive at the conclusion that "the project is achieving its stated goals". https://library.ctr.utexas.edu/Presto/content/Detail.aspx?ctID=UmVzZWFyY2gtaW4tUHJvZ3Jlc3NfMTExMjY%3D&rID=MjM3 https://library.ctr.utexas.edu/Presto/content/Detail.aspx?ct... PDF: https://tti.tamu.edu/documents/0-6688-1.pdf https://tti.tamu.edu/documents/0-6688-1.pdf -- It's possible that latent instead of induced demand was the cause, though. From another group from the institute: > Since its reconstruction, the improved capacity of IH 10 has been offset by latent traffic demand from commuters in the northwest and southwest utilizing IH 10 via Beltway 8 as an alternative to the heavy congestion on US 290 and US 59. This trend has been exacerbated since construction began on US 290 in 2011. https://mobility.tamu.edu/mip/congestion.php#houston https://mobility.tamu.edu/mip/congestion.php#houston PDF: https://mobility.tamu.edu/mip/corridors-pdfs/houston/HOU-22-IH-10-101713.pdf https://mobility.tamu.edu/mip/corridors-pdfs/houston/HOU-22-... -- There's not much more research beyond that--various news sources have cited traffic monitoring data as proof of continually worsening conditions. This 2015 piece from a think tank links to several local news articles and gives its own analysis: > We extracted these data from Transtar (Houston’s official traffic tracking data source) for two segments of the Katy Freeway for the years 2011 through 2014. They show that the morning commute has increased by 25 minutes (or 30 percent) and the afternoon commute has increased by 23 minutes (or 55 percent). https://cityobservatory.org/reducing-congestion-katy-didnt/ https://cityobservatory.org/reducing-congestion-katy-didnt/ Though, years after the lanes opened, that might just be population growth rather than induced demand. There's also a confounder in the US 290 construction, which didn't finish until 2017, but scrubbing through the TranStar data[1] I don't see a noticeable drop in congestion. But the talent agency post is from 2020; I still don't see why they feel the need to defend the project. [1]https://traffic.houstontranstar.org/hist/traveltimes_web_all.aspx https://traffic.houstontranstar.org/hist/traveltimes_web_all... ~~~~~ More links mostly for myself Portal for commuters: https://www.hctra.org/KatyManagedLanes https://www.hctra.org/KatyManagedLanes US and Texas Departments of Transportation on the concept of managed lanes: https://ops.fhwa.dot.gov/publications/managelanes_primer/ https://ops.fhwa.dot.gov/publications/managelanes_primer/ https://www.txdot.gov/driver/managed-lanes/managed-lanes.html https://www.txdot.gov/driver/managed-lanes/managed-lanes.htm...