{"id":86,"date":"2015-11-22T11:42:29","date_gmt":"2015-11-22T11:42:29","guid":{"rendered":"http:\/\/www.noisemap.ltd.uk\/wpress\/?page_id=86"},"modified":"2017-01-30T14:02:55","modified_gmt":"2017-01-30T14:02:55","slug":"roads","status":"publish","type":"page","link":"http:\/\/www.noisemap.ltd.uk\/wpress\/features\/roads\/","title":{"rendered":"Roads"},"content":{"rendered":"

\"\"<\/a>NoiseMap models and calculates road traffic noise using a method called ‘Calculation of Road Traffic Noise’ (CRTN).\u00a0 It was originally published in 1975 and was updated in 1988.\u00a0Further refinements have been\u00a0devised since then and these have also been incorporated into NoiseMap.<\/p>\n

CRTN calculates noise levels in terms of the LA10<\/sub> index.\u00a0This index has been largely superseded by the Equivalent Continuous Sound Level (LAeq<\/sub>).\u00a0 Fortunately, at locations alongside roads, these two indexes are highly correlated, which means that it is possible to predict the LAeq<\/sub> level from the LA10<\/sub> level with a high level of certainty.<\/p>\n

The UK government has published a procedure that allows LA10<\/sub> (18-hour) levels to be converted into Lden<\/sub> and Lnight<\/sub> values.\u00a0 Because motorways carry a higher proportion of traffic at night compared with other roads, the conversion factors for motorways are different from the conversion factors for other roads.\u00a0 NoiseMap also lets you calculate the noise levels for each hour of the day and to combine these to obtain averages over various time periods.\u00a0 This is particularly useful for ‘managed motorways’ where lane control is used to maximise the efficiency of the road, thus meaning that flows may deviate from the typical daily pattern.<\/p>\n

The CRTN methodology<\/strong><\/p>\n

Calculation of Road Traffic noise involves several steps.<\/p>\n

    \n
  1. Divide the road network into as many segments as necessary to ensure that there is uniform traffic and propagation conditions for each segment.\u00a0 In a large city, this could mean tens of thousands of road segments.\u00a0 The calculation method is then applied to each of these segments.<\/li>\n
  2. Calculate the noise generated by the traffic on\u00a0a segment at a notional reference location which is 10 m from the edge of the nearside carriageway and at a height of 1.2 m above it.\u00a0 This is the Basic Noise Level.<\/li>\n
  3. Adjust the Basic Noise Level to account for\n
      \n
    1. the distance of the receiver point from the road, (geometric spreading of the sound energy),<\/li>\n
    2. the height of the receiver point above the road and<\/li>\n
    3. the type of ground cover (ground effect, sometimes called \u2018ground absorption\u2019),<\/li>\n
    4. the effect of any intervening noise barriers and<\/li>\n
    5. the effect of reflecting surfaces.<\/li>\n<\/ol>\n<\/li>\n
    6. The calculation of the effect of barriers is particularly complex, as there can be many barriers between the road and the receiver, particularly in a city with many buildings.<\/li>\n
    7. The contribution from each segment is also adjusted according to the angle of view that it subtends at the receiver.<\/li>\n
    8. The contribution from all the road segments is then added to obtain the total noise level at the receiver.<\/li>\n<\/ol>\n

      This procedure gives the LA10<\/sub> value, which can then be converted to Lday<\/sub>, Levening<\/sub>, Lnight<\/sub> or Lden<\/sub> values using procedures published by the Government.<\/p>\n

      Click for more information.<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

      NoiseMap models and calculates road traffic noise using a method called ‘Calculation of Road Traffic Noise’ (CRTN).\u00a0 It was originally published in 1975 and was updated in 1988.\u00a0Further refinements have been\u00a0devised since then and these have also been incorporated into NoiseMap. CRTN calculates noise levels in terms of the LA10 index.\u00a0This index has been largely … Continue reading Roads<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":12,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/pages\/86"}],"collection":[{"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/comments?post=86"}],"version-history":[{"count":8,"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/pages\/86\/revisions"}],"predecessor-version":[{"id":669,"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/pages\/86\/revisions\/669"}],"up":[{"embeddable":true,"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/pages\/12"}],"wp:attachment":[{"href":"http:\/\/www.noisemap.ltd.uk\/wpress\/wp-json\/wp\/v2\/media?parent=86"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}