diff --git a/pyproject.toml b/pyproject.toml
index 51a6984e..81260ac9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -20,7 +20,7 @@ classifiers = [
 dependencies = [
     "pandas>=1",
     "matplotlib>=3.3",
-    "numpy>=1.18,<1.24",
+    "numpy==1.24",
     "scipy",
     "seaborn>=0.10",
     "typing_extensions",
diff --git a/rust/fastsim-core/src/simdrive.rs b/rust/fastsim-core/src/simdrive.rs
index c5e00146..26fcf0b6 100644
--- a/rust/fastsim-core/src/simdrive.rs
+++ b/rust/fastsim-core/src/simdrive.rs
@@ -36,11 +36,14 @@ pub struct RustSimDriveParams {
     pub time_dilation_tol: f64,
     /// number of iterations to achieve time dilation correction
     pub max_trace_miss_iters: u32,
-    /// threshold of error in speed [m/s] that triggers warning
+    /// threshold for triggering warning log message if vehicle speed deficit [m/s]
+    /// relative to prescribed speed exceeds this amount
     pub trace_miss_speed_mps_tol: f64,
-    /// threshold for printing warning when time dilation is active
+    /// threshold for triggering warning log message if achieved elapsed time
+    /// relative to prescribed elapsed time exceeds this fractional amount
     pub trace_miss_time_tol: f64,
-    /// threshold of fractional eror in distance that triggers warning
+    /// threshold for triggering warning log message if achieved distance
+    /// relative to prescribed distance exceeds this fractional amount
     pub trace_miss_dist_tol: f64,
     /// max allowable number of HEV SOC iterations
     pub sim_count_max: usize,
@@ -571,9 +574,16 @@ pub struct RustSimDrive {
     pub fc_kj: f64,
     pub net_kj: f64,
     pub ke_kj: f64,
+    /// `true` when the vehicle misses the prescribed speed trace
     pub trace_miss: bool,
+    /// fractional difference between achieved cumulative distance
+    /// and prescribed cumulative distance
     pub trace_miss_dist_frac: f64,
+    /// fractional difference between achieved time when trace miss is
+    /// and prescribed cumulative distance
     pub trace_miss_time_frac: f64,
+    /// Maximum speed by which vehicle's speed falls behind prescribed
+    /// speed trace
     pub trace_miss_speed_mps: f64,
     #[serde(skip)]
     pub orphaned: bool,
diff --git a/rust/fastsim-core/src/simdrive/simdrive_impl.rs b/rust/fastsim-core/src/simdrive/simdrive_impl.rs
index 38186339..4a94db7f 100644
--- a/rust/fastsim-core/src/simdrive/simdrive_impl.rs
+++ b/rust/fastsim-core/src/simdrive/simdrive_impl.rs
@@ -1853,8 +1853,9 @@ impl RustSimDrive {
         self.trace_miss = false;
         let dist_m = self.cyc0.dist_m().sum();
         self.trace_miss_dist_frac = if dist_m > 0.0 {
-            (self.dist_m.sum() - self.cyc0.dist_m().sum()).abs() / dist_m
+            (self.dist_m.sum() - dist_m).abs() / dist_m
         } else {
+            bail!("Vehicle did not move forward.");
             0.0
         };
         self.trace_miss_time_frac = (self