The Road Speeds dialog box is used to set the individual road speeds that MileCharter will use when calculating travel times. It is displayed by pressing the Speeds button on the main MileCharter dialog box, and looks like this:
By default, MileCharter will use Maptitude's own road speeds – indicated by the Override Maptitude Road Speeds check-box not being set. Set this check box if you wish to override the speeds. This will enable the table of road speeds. The road speed override status (overridden vs default) is displayed on the main MileCharter panel, to the left of the Speeds button.
The road speeds can be overridden with absolute speeds (as in the above table), or modified with relative adjustments. The table displays all of the road types detected in the current Maptitude map, along with default speeds and the current speeds. These are displayed using the current distance units per hour (miles per hour in the above example). Edit a road's speed by clicking on the Current Speed cell of the required road type (see Major County in the above example).
All of the speeds can be reset to their defaults by pressing the Reset to Defaults button.
Set the Relative Speed Adjustments if you wish to apply relative adjustments. Instead of replacing all roads of a specific type with the same speed, relative adjustments simply apply a ± percentage of Maptitude's own speeds. For example, a particular road type might be stored in the database with different speeds for different sections. These differences are retained, but merely modified up or down as requested.
Here is an example of the relative speed adjustments:
Most of the roads have not been modified, but the speed of the Major Interstate has been reduced by 50%, but the Major County roads have been increased by 100%. These are extreme examples – the Secondary Misc has been reduced by a more reasonable 6%.
Note that the travel time is a reciprocal of the speed. E.g. A decrease of 10% road speed, will result in an increase in travel time of 11% (1 ÷ 0.9). Here is table of example speed adjustments and how they influence the travel time:
You can set all of the road speed adjustments to the same percentage by setting the Reset Adjustments to value and pressing the Reset button.
The current speeds and relative speeds can be saved with the Road Parameters. They can also be restored from a Road Parameters file. This means you can create a 'driving profile' of costs and/or speeds that you can re-use or give to your colleagues.
The default speeds are derived from one of two places. MileCharter includes default speeds for a number of countries. These speeds are also published online. These were originally derived by finding the most common road speeds in the relevant Maptitude country data pack. These default speeds are used if they are available for the current country. If they are not available, Milecharter will scan Maptitude for all road types and representative speeds. Unfortunately it is a very time consuming process (30-90 minutes) to derive representative speeds. Therefore a quick (typically 2-3 minute) scan is performed that results in less accurate results. If you intend to modify the road speeds, it is recommended that you first check that all of the default speeds are reasonable.
MileCharter will perform this scan the first time you run it with road types that it does not recognize. You can also re-scan the road types by pressing the Rescan Maptitude Speeds button on the Road Speeds dialog box. Note: This button will not be displayed if MileCharter is using its own default speeds.
The scanning process can be annoying and the results are not necessarily very accurate. MileCharter's built-in default road speeds are more accurate and do not require a scan. They are currently defined for the following countries:
You can help us add the road speed information for your country to the next version of MileCharter by running our FetchRoadSpeeds utility and sending us the results. This can be downloaded here:
The scan process typically takes between 30 and 90 minutes, and results in a text file that you should email to us. The resulting road types and speeds for each country are also being published online at: