Appraisals should attempt to factor out any increase or decrease in value caused by project influence. Since the property to be acquired basically will no longer exist after the new facility has been provided, any increase in value which would have accrued to the property were it not a part of the facility should not be reflected in the estimate of value for the property. In other words, any increase in value because of the new facility should be disregarded in valuing the property before the acquisition, whether the whole or only a part is to be acquired. Likewise, except for the owner’s neglect, any decrease in value because the property is to be acquired for public use should be disregarded. The appraisers should be specifically instructed regarding such circumstances at the time the assignment is made.

This concept should also be applied to comparable sales. A number of sales on or near the project may occur which may include the influence of the project as reflected by an increase or decrease in value. The sale properties may have been comparable and may still “appear” to be comparable before construction; however, if the value has changed significantly, this is usually an indication that the highest and best use has changed because of the project. If this is true, the subject and the sales may not be truly comparable, even though they are physically similar, since they are or will be influenced by different outside factors.

The market before and after the project influenced the sales will need to be researched to estimate the extent of the adjustment. It should be noted, however, that it is very undesirable to use this type of sale in a condemnation trial to establish the value of the part being acquired. Therefore, every effort should be made to support the appraisal by sales not been influenced by the highway project.