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Measurement Sites 13 and 13A are located at an SFD which is one <br />house removed from the corner of Bristol at St. Gertrude. This <br />residence is. considered as a second line receptor since the comer house <br />provides shielding which would be eliminated if the house was removed <br />after right -of -way acquisition. Site 13 is located in the front yard at 70 <br />feet from the Bristol Street right -of -way. Site 13A is located in the rear <br />yard at an exterior activity area 90 feet from the Bristol Street right -of- <br />way. A 5.5 foot high wooden fence separates this rear yard from the <br />comer residential lot. From Table 8, it can be seen that noise levels at <br />Measurement Sites 13 and 13A are significantly lower than levels at the <br />first line receptor. <br />Noise from motor vehicles is generated by the engine vibrations, the <br />interaction between the tires and the road, and the exhaust system. <br />Reducing the speed of motor vehicles reduces the noise exposure of <br />listeners inside the vehicle and those located adjacent to the roadway. <br />The highway traffic noise prediction model developed by the Federal <br />Highway Administration (RD -77 -108) and currently being applied <br />throughout the nation was used to evaluate current noise conditions at <br />various points along Bristol Street within the project area. This model <br />accepts various parameters including; the traffic volume; vehicle mix <br />and speed; and roadway geometry in computing equivalent noise levels <br />during typical daytime, evening, and nighttime hours. <br />The resultant noise levels can then be weighted, summed over 24 hours, <br />and output as' the CNEL value. Various CNEL contours are <br />subsequently located through a series of computerized iterations w <br />designed to isolate the critical contour locations. Noise contours were <br />developed as a planning tool for local agencies. ` <br />' Cp <br />