There has been an ongoing debate on whether telecommuting increases or decreases traffic. These effects are usually studied based on travel diary data from household travel surveys. Previous research shows that survey period can influence measures of travel behaviour. However, it is unclear if this also holds true when measuring the influence of telecommuting on travel behaviour.

We analysed how the survey period of travel diaries affects estimates of telecommuting effects on travel behaviour measures. Our results show that an increased telecommuting frequency has a negative effect on the number of trips conducted regardless of the survey period. However, there is a significant influence of the survey period when measuring the effect of work from home on person kilometers travelled. While the baseline estimator for the telecommuting frequency is negative, this only holds true for the 1-day survey. The effect becomes positive when considering the 1-week survey influence. These findings lead us to conclude that studies based on 1-day trip diary data will likely overestimate traffic reduction potential of telecommuting measures and results from such studies should be interpreted with caution. The results are of interest to policy makers as they assess the influence of telecommuting on travel demand.