Does a driver's failure to maintain his lookout constitute negligence as a matter of law?

Thus we find on the question of negligence or contributory negligence of a party as a matter of law that if the party involved did exercise some care, the question of whether or not that care was all that an ordinarily reasonable person would have taken under the circumstances of the case continues to be a question of fact for determination of the court or jury. As was said in Kalfus v. Fraze, 136 Cal.App.2d 415, 430, 288 P.2d 967, 977:

'Although the general rule is that a driver's failure to maintain such lookout as would enable him to observe all that may be readily seen may constitute negligence as a matter of law (citations), where, as in the present case, the driver testifies that he did in fact look, the question of whether he looked with proper care and saw all that he should have seen is one of fact for the determination of the court or jury.'

In Startup v. Pacific Electric Ry. Co., 29 Cal.2d 866, 871, 180 P.2d 896, 899, the court said: