Reducing traffic pollution

Here’s some solutions that can help to reduce a significant part of the problem (traffic pollution).

Solutions to Traffic Pollution in the 21st Century

  • a concise introduction to traffic pollution
  • concise strategies to reduce traffic pollution

Ideally, we should phase out diesel (and other combustion powered) vehicles as quickly as possible. In the meantime, here is an intermediate opportunity…

Reducing toxic emissions from diesel powered vehicles
(PDF, 358kB)

Thank you @akb! We’ll be sure to make a look at these.

The link to Solutions to Traffic Pollution includes the following recommendations:

» Create pedestrian only areas, especially where there are lots of people.

» Implement low emission zones: areas for low, or zero, emission vehicles only.

» Set up areas where diesel vehicles are not allowed. This could be challenging for deliveries though; so perhaps schedule deliveries outside of busy periods and/or encourage a new zero emission urban logistics service.

» Modify diesel vehicles with technologies that improve their emissions. [see PDF]

» Switch bus fleets from diesel to gas, alcohol, hydrogen or electric power.

» Target the worst 10 percent of vehicles (which can cause up to half of all the pollution). At the simplest level, this could be enforced by police and traffic wardens by recording the number plates of smoking vehicles, and sending their owners warning letters then fines for repeat offenders. More advanced solutions are available based on the use of technology.

In the comments below are suggestions for how modern technology and innovation could help with some of the above recommendations…

Pedestrian only areas
In reality, we sometimes see vehicles in pedestrian areas because: (a) some vehicles have exemptions and are allowed access (e.g. deliveries, utilities, security vans, and vehicles carrying disabled people); or (b) vehicles that are in violation of the pedestrian area.

Artificial intelligence, in conjunction with suitably placed cameras, could be trained to learn which vehicles are allowed access and which are not. (This may also involve the use of (in-screen) badges, such as those used by disabled drivers/passengers.) By reading car number plates fines could be automatically distributed to those that violate pedestrian areas.

Another technology also offers a solution: vehicle transponders, which use radio frequency IDs (RFID). These have been used on toll roads to make automatic charges, and they can be readily deployed to this scenario. A database of authorised IDs would be used to determine if a vehicle is authorised.

Low emission zones
Similar technology to that above (pedestrian areas) can be used to control access to a low emission zone.

In addition, a low emission zone might be dynamic: the restriction might be activated at given times of the day, when monitored pollution levels exceed limits, or when predicted pollution levels are expected to exceed limits.

In the latter case representative historical traffic patterns are fed into a computer model to predict emissions, and with meteorological forecasts a dispersion model predicts pollutant concentrations on each street. If predictions are conducted one day (or more) in advance then the public can be notified (online and via media channels) in advance - thus allowing travel plans to be adapted accordingly. [Details of this approach can be found in Prediction and reduction of traffic pollution in urban areas.]

A low emissions zone could be enforced on the basis of actual vehicle emissions. This has the benefit that modern vehicles that supposedly meet the emissions criteria can be detected when they are poorly maintained and emit excessive levels of pollution - you might have seen new diesel vehicles doing this. The technology to do this involves a camera (to catch the vehicle’s number/license plate) and a pollution sensor that detects actual emissions from the exhaust pipe as vehicles drive past. One technology to do this uses a laser beam. Such an approach would be useful for detecting excessive levels of particulate emissions from the offending vehicles. Given that 10% of the vehicle fleet can produce up to 50% of total emissions this can be an effective approach for cleaning up urban air quality.

Hi @JessicaYoon I’ve added a few more comments above.

Hi @Jeff, @jd_sabikeshare, @jslavin, @UM2100,
Given your area of expertise, we would love to hear your thoughts on innovative ways to reduce air pollution due to vehicles.

@akb Very nice summary of strategies, many that we’ve tried here in California. Here’s what seems to be the most effective, in priority order:

  • Fuel changes (e.g., lead-free gasoline, benzene limits, low aromatic diesel) lead to immediate air quality benefits. See [Cleaner-Burning Gasoline: An Update (CARB)](
  • Three-way catalyst on gasoline-fueled vehicles enabled by low sulfur gasoline fuel (>99% control, now implemented world wide). See [Warneke et al. (2012) Multiyear trends in volatile organic compounds in Los Angeles, California: Five decades of decreasing emissions](
  • Catalyzed diesel particle traps enabled by low sulfur diesel fuel (99% control, mandatory retrofits and replacement implemented in California because of slow natural turnover). See [Propper et al. (2015) Ambient and Emission Trends of Toxic Air Contaminants in California](
  • Inspection and Maintenance program (periodic testing on dynamometers) augmented by remote sensing to go after high-emitting vehicles. See [Bishop and Stedman (2008) A Decade of On-road Emissions Measurements](
  • Electric cars and buses.
  • Siting schools, day care centers, playgrounds, and housing 500 feet or more from freeways, urban roads with 100,000 vehicles/day, or rural roads with 50,000 vehicles/day. See [CARB (2005) Air Quality and Land Use Handbook: A Community Health Perspective](
  • Seven effective startegies supported by peer-reviewed studies. See [CARB (2017) Technical Advisory: Strategies to Reduce Air Pollution Exposure Near High-Volume Roadways](
  • We haven’t tried low-emission zones (yet) that have been effective in London and Germany, mostly because we’re focused on cleaning up all vehicles.

    Our current research is focused on the health effects and emission control technologies for brake- and tire-wear, engine wear, and road wear (we’ve been unable to regulate friction :wink: and noise.

    Note that near-roadway dust and vehicle component wear dominates over tailpipe PM in California, but only because we’ve put a filter on all diesel engines. Tailpipe emissions, especially from diesel vehicles, will dominate elsewhere and more cost-effective diesel control technologies are still needed. The incremental cost for catalyzed diesel particle filters is $5k-$15k per on-road truck, and up to $50k for non-road (e.g., construction) equipment. Ultra-low sulfur diesel fuel is also needed, which needs large capital investments for refineries recovered through a 5-15 cents per gallon incremental cost. While the US, EU, and some Asian countries require these technologies and are making these investments, it’s not affordable for many others.

    Dear Professor Bart, A few vehicle anti-pollution ideas here, that I have already sent all over the Internet with few replies:
    1-Modify all of the ‘dirty’ diesel fuel burning semi trailer trucks, with a type of Nanotube Air Filter, (Which is now installed in ALL passenger airliner planes, to separate pure Oxygen and pure Nitrogen from outside air, in order to provide INERT Nitrogen gas, to pump inside of the plane’s emptying fuel tanks, so that static electricity cannot spark an explosion!) that provides a lot of PURE OXYGEN, to pump into a fuel/as ratio modified diesel engine, to enable the engine to COMPLETELY burn up the dirty diesel fuel without any atmosphere exhaust particulates, and get better truck mileage as well.
    2-Consult with a ‘Land Art Initiative’ movement, that makes these BEAUTIFUL kinds of windmills, that they incorporate into urban settings. Their idea is to use the windmills to generate clean electricity inside of the cities where it’s needed. But, this never caught on, apparently because it would require a major rewiring of our cities electric power grids. We actually need that anyway, but at this rate, I doubt if it will ever happen! But, what if we installed these pretty windmills anyway, only, they propel air pumps, which will suck outside city air, and its pollution particulates, into CHEAP but effective ‘Jute paper ‘coffee filters’, which India can provide us with, to clean the city air? The pumped air would then be channeled through buried hoses, or tubes snaked through local sewer lines, to buildings where the propelled air (This only works for SHORT distances, compressed air is NOT a great vector of kinetic energy, but it could work in "Dense Pack’ cities or towns, like here in New Jersey, effectively.) turns a turbine to turn an electrical generator. This set up could provide electric power, to supplement the use of electric cars in our cities, to further reduce local air particulate pollution.
    3-GOLD Air Filters? Professor Bart, has anybody ever looked into using the metal Gold, to create a new kind of air or water filter? Gold has a very high tensile strength, and we can use modern Nanotechnology now, to make gold sheets only 2 ATOMS in thickness! (An old school science project, is to shine a lantern through a gold leaf sheet, and a BEAUTIFUL green light shines from it. But, I don’t know if this green light effect could help to purify water or air.) and it is electrically conductive. This means that we could use PEBs (Particle Emission beams) to punch super tiny holes in this Gold leaf sheet, and pass electricity through it, while passing polluted air or water through it. The electrical charging MIGHT burn up carbon-based air particulates, or create an electrostatic effect to make air soot slide off the gold face mask or whatever, or prevent salt in sea water from passing through this gold filter, because salt water is also electrically conductive. And, if this idea ACTUALLY works, remember, this is a THIN filter, so very little expensive gold would be required to make them! And unlike other types of filters, we could take the clogged up gold filters, and simply melt them down, to recycle this gold element into re-castings of new filters. BUT, I am not an expert in this field, I am throwing spitballs at you here, OK? Please forward this idea to the REAL experts in this field. Thank you, Best Regards, Robert Schreib

    Thank you @bartc