A road pricing model is presented that determines tolls for congested highways. The main contribution of this paper is to include density explicitly in the pricing scheme and not just flow and time. The methodology solves a nonlinear constrained optimization problem whose objective function maximizes toll revenue or highway use (2 scenarios). The results show that the optimal tolls depend on highway design and the level of congestion. The model parameters are estimated from a Chile’s highway data. Significant differences were found between the highway’s observed tolls and the optimal toll levels for the two scenarios. The proposed approach could be applied to either planned highway concessions with recovery of capital costs or the extension or retendering of existing concessions.

<b><i>Background:</i></b> Caffeine is a commonly used drug for apnea of prematurity. It may, however, also have a beneficial effect on bronchopulmonary dysplasia (BPD), which is the most common complication of extreme preterm birth. <b><i>Objectives:</i></b> To study the inflammatory, structural and functional effects of caffeine in an animal model of BPD. <b><i>Methods:</i></b> Preterm New Zealand-Dendermonde rabbits (gestational day 28; term 31) were randomized to three groups: normoxia-placebo (N-P), hyperoxia-placebo (H-P) and hyperoxia-caffeine (H-C). Lung function was assessed on postnatal day 5, along with airway morphometry, vascular morphometry and a score observing airway inflammation. <b><i>Results:</i></b> Caffeine improved lung function by increasing lung volume [mean displaced volume N-P: 40.1 ± 6 ml/kg, H-P: 27.8 ± 8 ml/kg and H-C: 34.4 ± 7 ml/kg (p < 0.05); total lung capacity: N-P: 1.17 ± 0.1 ml, H-P: 0.67 ± 0.1 ml and H-C: 1.1 ± 0.1 ml (p < 0.05)], decreasing tissue damping [N-P: 2.7 ± 0.3 cm H₂O/ml, H-P: 4.6 ± 0.6 cm H₂O/ml and H-C: 3.2 ± 0.4 cm H₂O/ml (p < 0.05)], elastance [N-P: 9.3 ± 2.4 cm H₂O/ml, H-P: 19.2 ± 7.4 cm H₂O/ml and H-C: 10.7 ± 2 cm H₂O/ml (p < 0.05)] and compliance [N-P: 0.06 ± 0.01 cm H₂O/ml, H-P: 0.054 ± 0.01 cm H₂O/ml and H-C: 0.07 ± 0.013 cm H₂O/ml (p < 0.05)]. Caffeine also improved histology by decreasing alveolar size [linear intercepts; N-P: 83.6 ± 1.7, H-P: 82.9 ± 1.6 and H-C: 67.3 ± 1.4 (p < 0.05)], increasing radial alveolar count (N-P: 6.6 ± 0.5, H-P: 5.7 ± 0.6 and H-C: 7.05 ± 0.5) and decreasing the acute inflammation score [N-P: 0.3 ± 0.1, H-P: 0.5 ± 0.1 and H-C: 0.4 ± 0.1 (p < 0.05)]. <b><i>Conclusion:</i></b> In preterm rabbits, caffeine reduces the functional, architectural and inflammatory pulmonary changes induced by hyperoxia in the lung.