Using incentives as traffic management tool: empirical results of the "peak avoidance" experiment

Ettema, Dick; Knockaert, Jasper; Verhoef, Erik · 2010 · OpenAlex-citations

DOI: 10.3328/tl.2010.02.01.39-51

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Summary

This paper evaluates the effectiveness of positive incentives as a traffic management tool through the Dutch “Spitsmijden” (Peak Avoidance) experiment. While road pricing is a recognized method for reducing congestion by internalizing external costs, its implementation is often hindered by public resistance and equity concerns. The authors investigate whether positive rewards can achieve similar behavioral shifts—specifically, shifting car trips away from peak hours—without the negative perceptions associated with tolls. The study aims to determine the magnitude of behavioral change induced by different incentive types and sizes, and crucially, whether these changes persist after the incentives are removed. The experiment was conducted from September to November 2006 on the A12 motorway between Zoetermeer and The Hague, a heavily congested commuter corridor. Approximately 340 daily commuters were recruited via license plate recognition. Participants were assigned to one of two incentive strategies: a financial reward scheme or a non-monetary reward scheme. In the financial group, participants received €3 or €7 per day for avoiding the 7:30–9:30 AM peak by car, with variations in reward structure tested over ten weeks. In the non-monetary group, participants earned credits toward a Yeti smartphone (valued at ~€600) for peak avoidance. Behavior was monitored using high-accuracy transponder detection systems (99.8% detection rate) and participant diaries to record mode choice and timing. Data were collected during pre-measurement, the incentive period, and post-measurement phases to assess sustainability. The results demonstrate that positive incentives significantly reduced peak-period car travel. Participants reduced their share of car trips during the peak hours by approximately 60%, dropping from roughly 50% in the pre-measurement phase to 19–26% during the incentive period. This reduction was primarily achieved through temporal shifting; travelers moved their car trips to before 7:30 AM or after 9:30 AM, rather than switching modes. Public transport use increased modestly, from 3.9% to between 9.5% and 12.0%, while cycling and teleworking saw minor increases. The financial incentive of €3 produced the largest initial shift, with higher or variable rewards yielding only marginal additional reductions. However, the behavioral changes were not sustainable. Once the incentives ended, participants returned to their pre-experiment travel patterns, with peak car usage reverting to approximately 47–50%. The study concludes that while positive incentives are effective at inducing immediate peak avoidance, they do not lead to structural, long-term changes in travel behavior. The findings suggest that incentives function as a temporary motivator rather than a tool for permanent habit formation. Furthermore, the primary response was time-shifting rather than mode-shifting, indicating that travelers prefer to maintain their preferred mode (car) while adjusting timing to capture rewards. These results imply that incentive-based strategies may be useful for short-term traffic management but are insufficient for achieving lasting congestion reduction without complementary measures that address underlying constraints and preferences.

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• gamification driving