Editing Highway (section)

== Economic effects ==
{{Main|Transport economics}}
In transport, [[Demand (economics)|demand]] can be measured in numbers of journeys made or in total distance travelled across all journeys (e.g. [[passenger-kilometre]]s for [[public transport]] or vehicle-kilometres of travel (VKT) for [[private transport]]). [[Supply (economics)|Supply]] is considered to be a measure of capacity. The [[price]] of the good (travel) is measured using the [[generalised cost]] of travel, which includes both [[money]] and [[time]] expenditure.
[[File:Leipzig-Halle Airport Condor.jpg|thumb|right|A taxiway crossing the [[Autobahn]], near Leipzig]]

The effect of increases in supply (capacity) are of particular interest in transport economics (see [[induced demand]]), as the potential environmental consequences are significant (see ''externalities'' below).

In addition to providing benefits to their users, transport networks impose both [[positive externalities|positive]] and [[negative externalities]] on non-users. The consideration of these externalities—particularly the negative ones—is a part of transport economics. Positive externalities of transport networks may include the ability to provide [[emergency services]], increases in [[land (economics)|land]] value and [[economies of agglomeration|agglomeration benefits]]. Negative externalities are wide-ranging and may include local [[air pollution]], [[noise pollution]], [[light pollution]], [[traffic safety|safety hazards]], [[community severance]] and [[traffic congestion|congestion]]. The contribution of transport systems to potentially hazardous [[climate change]] is a significant negative externality which is difficult to evaluate quantitatively, making it difficult (but not impossible) to include in transport economics-based research and analysis. Congestion is considered a negative [[externality]] by economists.<ref>{{Cite book |last1 = Small |first1 = Kenneth A. |first2 = José A. |last2 = Gomez-Ibañez |name-list-style = amp |year = 1998 |title = Road Pricing for Congestion Management: The Transition from Theory to Policy |publisher = The University of California Transportation Center, University of California at Berkeley |page = 213 }}</ref>

A 2016 study found that for the United States, "a 10% increase in a region's stock of highways causes a 1.7% increase in regional patenting over a five-year period."<ref>{{Cite journal |title = Roads and Innovation |journal = The Review of Economics and Statistics |volume = 99 |issue = 3 |pages = 417–434 |doi = 10.1162/REST_a_00619 |year = 2017 |last1 = Agrawal |first1 = Ajay |last2 = Galasso |first2 = Alberto |last3 = Oettl |first3 = Alexander |s2cid = 7268833 }}</ref> A 2021 study found that areas that obtained access to a new highway experienced a substantial increase in top-income taxpayers and a decline in low-income taxpayers. Highways also contributed to job and residential urban sprawl.<ref>{{Cite journal|last1=Fretz|first1=Stephan|last2=Parchet|first2=Raphaël|last3=Robert-Nicoud|first3=Frédéric|date=2021|title=Highways, Market Access, and Spatial Sorting*|url=https://doi.org/10.1093/ej/ueab070|journal=The Economic Journal|volume=132 |issue=643 |pages=1011–1036 |doi=10.1093/ej/ueab070|issn=0013-0133|hdl=10419/173046|hdl-access=free}}</ref>