The level of toxic emissions from vehicles along a road depend on a number of variables:

• The proportion of LIGHT DUTY and HEAVY DUTY vehicles (The latter can typically emit 25 times the toxins of the former)
• The peak hour traffic flow (how many of each type pass a point in the peak hour)
• The age of the vehicles ( more modern vehicles emit less toxins)
• The speed of the vehicles (slow and fast moving vehicles emit more toxins than those travelling at around 40-50 mph)
• The distance from the road of the measuring point
• The type of toxin ( NO2; Particulates; CO; Benzine)

Through experiments and mathematical modelling, a table of emissions at varying distances from a road was drawn up. It is based on a standard traffic flow of 1000 vehicles an hour moving at 100 km/hour.

For each road under consideration, the level of toxin at the specified distance is read from the table. Then the figures are adjusted for each varying factor (e.g. average speed of traffic, year etc.)

The effect for each road under consideration are then totalled, and the results interpreted.

Below we have devised a simplified model so that you can roughly calculate the Nitrogen Dioxide level for any point in Bingley within 200m of the roads. Only traffic along Bingley Main St. and the new Relief Road are considered. You should print out the form.

All predictions for traffic flow levels etc. are taken from those used by Bradford Council.

The value of toxin level for any point further than 200m can be taken to be zero.

In order to work this out you will need:

• A good map to measure the distance from your point to the centre of the two roads at their nearest point.
• A calculator
• An ability to read values from a graph.

Additional Info is provided at several points - click the link.

The figures derived in step 6 are the NO2 hourly average values (98%ile) as used in the results of the Council and our own modelling exercise.

Step 2: These values are taken from the standard data table (fig 2, Vol 11, Section 3, Part 1) and show emission concentrations produced by 1000 veh/hr travelling at a speed of 100 km/hr as a function of the distance from the road.

Plot the distance along the bottom of the graph, read straight upwards to the graph line, then follow straight across to the left to read off the Nox (ppb) reading for the stated distance factor. (Back to calculator)

Step 4: The emission factor (NO2) here is a combination of various factors worked out in advance for given traffic flows in Bingley in the year 2000: They are based on the following:

NO RELIEF ROAD:

• Peak hour traffic flow on Main St.: Light vehicles - 1760; Heavy vehicles - 140; average speed - 30 km/hr.
• Emission correction factor (year): Light - 0.536; Heavy - 3.58
• Speed correction factor: Light - 0.91; Heavy - 1.10

WITH RELIEF ROAD:

• Peak hour traffic flow on Main St.: Light vehicles - 810; Heavy vehicles - 80; average speed - 35 km/hr.
• Emission correction factor (year): Light - 0.536; Heavy - 3.58
• Speed correction factor: Light - 0.83; Heavy - 1.06
• Peak hour traffic flow on Relief Rd.: Light vehicles - 2270; Heavy vehicles - 90; average speed - 80 km/hr.
• Emission correction factor (year): Light - 0.536; Heavy - 3.58
• Speed correction factor: Light - 0.79; Heavy - 0.70

Simply multiply the Distance factor by the emission factor. (Back to calculator)

Step 5: With the Relief Road, the contribution to emission levels from both roads needs to be added together. (Back to calculator)

Step 6: The results of the calculations so far give us the adjusted Peak Hour Nitrogen Dioxide Levels (ppb). These now need to be converted to the Normal hourly averages (98%ile) as used elsewhere. This is done with Chart 2. Find the Peak Hour level along the bottom of the graph, trace straight upwards to the graph line, then move straight across to the left to find the appropriate figure. (Back to calculator)

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