How do I input Ldn and Lden data in TNM?
(Applies to TNM version 1.0, 1.0b, 1.1, and 2.0) In versions previous to 2.1, TNM automatically assumes a 50/50 split of ADT between day and night for Ldn and a 33/33/33 split of ADT between day, evening, and night for Lden. It is recommended that users not use Ldn and Lden but instead modify Equation 15 on Page 66 in the TNM Technical Manual to compute equivalent hourly volumes. The equivalent volumes would give a LAeq1h that is actually a DNL or CNEL. Then input this as LAeq1h traffic type. (Note: When using Equation 15, %day + %evening + %night = 100%; for input to TNM, %day = %evening = %night = 100%). Also keep in mind that although lane-by-lane speed and volume is not necessary, HOV and truck restricted lanes should be implemented. * Calculations for Ldn and Lden have been modified to incorporate more representative numbers of hours in TNM Version 2.1. Only if your total hourly traffic volumes are the same for each hour of the day, this modification will now produce more represen
