Most road scheme assessments need you to compare noise levels in different years, sometimes with a new road scheme, and sometimes without. Traffic flows will be different in these various scenarios.
However, when putting together your table of traffic flows,
always try to ensure that the same segment of road has the same traffic flow id number in each scenario.
Suppose you are dealing with a bypass scheme. In the baseline situation, there two roads, Main Road and Side Road. Assign these traffic flow id numbers 11 and 12 for example. In the future situation, there is also the new road, called ByPass. Assign an different traffic flow id number to this, say 150. (The actual numbers are not important.) Then for the baseline you would have a flow table as follows:
Baseline| Flow ID | Name | Flow Rate | etc |
| 11 | Main Road | 15430 | etc |
| 12 | Side Road | 3680 | etc |
And for the
Future, you have:
| Flow ID | Name | Flow Rate | etc |
| 11 | Main Road | 5290 | etc |
| 12 | Side Road | 2850 | etc |
| 150 | Bypass Road | 25230 | etc |
You save the old and new situations to different scenarios, and NoiseMap keeps the same flow id numbers in the new scenario. So by using the same flow number, NoiseMap will simply replace the old flow rates with the new ones.
You save a lot of time and avoid errors because you do not have to work out which new flows belong to which segments. And if you have to revise the flows later on, this will be much easier.
