# Day and Night: Locating the General Practitioner's Panel after Hours
## 4 Discussion  
In the Halifax setting, the absolute distance travelled differed little (less than 1% difference) between solution approaches when using the same number of facilities. In terms of distance travelled per person, the largest difference in cost was in the magnitude of tens of meters, which may be considered marginal when looking at a population of hundreds of thousands of people.  
However, this result is unsurprising when considering certain details of the study. Foremost, the demand assigned at each node was considered to be the same for both the day and after hours. The difference between settings is the number of facilities located, and the difference between models are the constraints used to restrict facility location. When most of the model parameters are homogeneous across the time setting, it is logical that each approach results in a similar cost.  
It is also necessary to consider that the region of study contains urban and rural areas with very different population densities. While the total solution cost may not have changed much on average per person between approaches, this is likely not distributed equally among demand. If a large portion of this cost discrepancy was due to lower distance travelled by people in rural areas, this could mean a much larger difference for those people since there are fewer of them than the urban population. This could mean that the model has a more pronounced effect on the rural population than is apparent when considering urban demand in the average denominator. It is also worth noting that the large portion of people who live in the dense, urban part of Halifax will never be more than a kilometer or two away from a PCP, and optimising for geospatial access is likely best applied to rural demand, where the population density is lower and services are farther away.  
Another important result is that each solution approach performs relatively as expected. The independent approach represents a naive scenario where both the day and after-hours facility locations can be treated independently with no cost, and this approach always had the lowest total cost. Conversely, the more constrained approaches had higher costs, with the most constrained approaches (the sequential RtA and AtR approaches) resulting in higher cost solutions. While this was expected, an interesting result was that which sequential approach was better depended on the test conditions. The regular-to-after-hours approach yielded worse results in most cases, which is noteworthy since this is the most likely real-world method for determining facility locations.  
For the Halifax tests, each solution approach provided the same result when the number of regular and after-hours facilities were the same. Since the demand in these tests was identically located across both time settings, it makes sense since the same solution would be identical for both settings. However, in the modified Cape Breton setting, this was not the case. Since the demand differed between time settings in these tests, a difference could be observed in the efficacy of each approach (seen in Figure 9).