Taking advantage of the panel data, we formalized this approach in the following regression: hc = H h<sup>+ ∑</sup> T c T c hc hc (Equation 1) TT cc=2 cc cc hcc<sup>) + λλXX+ εε</sup> where YY denote household, commune, and time, respectively. γγ δδ + ββT TT + κκ(T TT ∗FFH δt denotes dummy variables for each year; H h<sup>is a household fixed effect,11 andXX</sup> hc<sup>are time-variant household characteristics.FFH</sup> h<sup>is a</sup> h, cc, TT dummy variable equal to one if a household head is a woman, and zero otherwise. hc includes controls for the age of the household head, the number of dependents in the household<sup>12</sup> and the level of XX education of the household head. hc captures outcomes of interest, such as household production and trade of crops and livestock, the types of crops grown, and the inputs into production, as well as measures of welfare like income, quality YY of housing, and consumption at the household level. We also explore the impact on employment at the individual level. These outcomes represent the overlap between the outcomes where we expected changes based on the literature and the data available in the VARHS. The parameter of interest in equation (1) is the coefficient on the dummy T T c which takes the value of one when the treatment is active. In contrast to the existing literature where road improvements are TT treated as permanent, given the nature of the RTP3 project, we treat improvements as temporary. Following consultation with transport specialists at the World Bank and corroboration by specialists from the DRVN and the Transport Development and Strategy Institute (TDSI) in Vietnam, we arrived at the following as an average estimate of the life span of each type of RTP3 activity:

- **Routine maintenance** leads to an improvement in road quality that lasts a maximum of one year since these activities typically prevent road quality from deteriorating during the rainy season. We use one year as the life span of a road improved with routine maintenance.

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- **Periodic maintenance** leads to improvements that last longer, typically around two years.<sup>13</sup>

- **Rehabilitation** improves road quality<sup>14</sup> for longer than five years, the maximum length of the postintervention period in our study, so we treated it as a permanent improvement _within our study period_ (i.e., a road rehabilitated in 2009 remains “improved” until 2014). This is consistent with

> 11 Since we had household-level fixed effects and the households in our sample did not move in the duration of the study, these absorbed a potential commune-level fixed effect.

> 12 We controlled for number of dependents in the household rather than household size. The number of dependents likely correlated with the household size, but did not open up a channel for omitted variable bias arising from the fact that household size is affected by migration caused by road improvements.

> 13 The administrative data do not distinguish between periodic maintenance on unsealed and sealed roads. The lifespan of this intervention on sealed roads is usually longer, up to six to eight years. Therefore, the average lifespan proposed by transport specialists at the World Bank, DRVN, and TDSI is a conservative estimate of the duration of improvement.

> 14 As noted in Section 2, activities classified in the administrative data as “road rehabilitation” include rehabilitation and upgrading. The life span for upgrading is typically much longer than six years, whereas for rehabilitation, improvements are normally expected to last on average five years.

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